Method and apparatus for displaying data in a medical imaging system

ABSTRACT

A system for acquisition, processing and display of gated SPECT imaging data for use in diagnosing Coronary Artery Disease (CAD) in nuclear medicine. The present invention provides a physician with two parameters for evaluating CAD: information relating to the distribution of blood flow within the myocardium (perfusion) and information relating to myocardium wall motion (function). One aspect of the present invention provides the physician with a display of functional images representing quantitative information relating to both perfusion and function with respect to selected regions of interest of the subject heart at end-diastole and end-systole segments of the cardiac cycle. The functional display consists of arcs of varied width depending on wall motion and color coded to illustrate degrees of myocardial perfusion for different pie shaped sections of a selected region of interest within a given short axis slice of reconstructed volume data. The present invention also provides a series of display images allowing facilitated access, display, and comparison of the numerous image frames of the heart that may be collected during gated SPECT sessions. The present invention also offers the ability to define and recall parameter files representative of data acquisition and processing parameters and protocol for use in gated SPECT studies. The invention also includes a semi-list processing mode to increased efficiency of data acquisition within a camera computer system.

This is a divisional of application Ser. No. 08/393,447, filed Feb. 231995 now U.S. Pat. No. 5,722,405, which is a divisional of applicationSer. No. 08/048,751, now U.S. Pat. No. 5,431,161 filed Apr. 15, 1993.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to the field of nuclear medicine camerasystems. More specifically, the present invention relates to the fieldof nuclear medicine camera systems utilizing gated SPECT acquisitiontechniques.

(2) Prior Art

In an attempt to more accurately diagnose Coronary Artery Disease (CAD)and generally diseases of the heart, specialized nuclear medicine camerasystems have been developed to provide physicians with vital informationregarding the structure of the heart and myocardial wall tissue. Theimages of the heart structure provided by these non-intrusive nuclearmedicine camera systems illustrate tissue and structure that would notbe otherwise visible without the application of nuclear medicine orother non-intrusive method. Gamma cameras of the Anger type are wellknown cameras in the field of nuclear medicine. These cameras receiveenergy emissions from a radio-pharmaceutical that is introduced into apatient and concentrates or localizes within the organ or tissue ofinterest for imaging. Such cameras are used extensively in nuclearmedicine as radiation detectors for establishing the distribution of theradio-pharmaceutical within the organ or tissue of interest. Such acamera is described in detail in U.S. Pat. No. 3,011,057 issued to Angerin which a typical gamma camera apparatus is disclosed for collectinginformation after introduction of radionuclides via inhalation,injection or ingestion.

Single Photon Emission Computerized Tomography (SPECT) is a type ofnuclear camera imaging system wherein the radiation detector of thecamera system is rotated about an organ or tissue (referred as an objectof interest) and images of the object of interest are recorded atdiscrete angles of rotation. By projecting back each image of the objectat these different rotation angles, a total image or reconstructedvolume can be generated and images may be observed at different sliceswithin the object volume itself. In other words, three dimensional imageinformation can be generated by SPECT camera systems of the object ofinterest Typically the camera detector rotates 180 degrees or full 360degrees around the object (patient) during the image acquisition phaseof the SPECT camera system Once the image data is collected by thecamera system, it is processed by a computer system where the tomographyis performed and the images may be generated qualitatively and studiedon a computer display screen. Such SPECT camera systems are well knownin the art of nuclear medicine.

With respect to prior art SPECT camera systems used in non-gated cardiacperfusion studies, heart tissue is studied for infarct areas andischemic areas by examining the heart under two different conditions, astress condition and a rest condition. Perfusion refers to the bloodflow to the heart in the areas of interest. The radionuclide introducedto the heart will follow the blood flow and thus perfusion is determinedby monitoring the resultant radiation from the radionuclide. An infarctarea is an area of the heart that is not functional and may be composedof dead tissue. This area may not take up much if not any of theintroduced radio-pharmaceutical. An ischemic area of the heart is anarea that may perhaps function normally during rest conditions, but willnot function normally during cardiac stress conditions. In order todetect an ischemic area, non-gated SPECT systems must collect image dataat cardiac rest and stress conditions, requiring two sessions.Therefore, according to the two conditions under study as describedabove, the ischemic area will be detected by comparing the images of theheart during the stress condition and the rest condition. In this priorart system, SPECT camera systems are used to examine the heart after theheart is subjected to a stress condition, typically by having thepatient run a treadmill. The heart imaging session of the prior artcamera systems takes approximately 30 minutes. Next, the patient isallowed to rest for at least four hours and a new imaging session isperformed on the heart during a rest condition. The physician thencompares the results of the imaging at rest and at stress. An ischemicarea may show up as a myocardial defect on images of the heart takenduring stress conditions but may show up normally on images of the hearttaken during rest conditions. An infarct area should show up as a defectin the heart at both rest and stress conditions.

The above prior art non-gated SPECT perfusion method for determiningCAD, such as infarct areas and ischemic areas, is not the mostadvantageous system. This is the case because two imaging sessions mustbe performed in order to adequately detect and diagnosis cardiacdisease. For instance, a cardiac rest session and a cardiac stresssession are required in the prior art that consume at minimum 30 minutesper session. Further, the patient must be allowed to rest for at leastfour hours in between cardiac stress/rest sessions. Taking in to accountpreparation and analysis time, the entire non-gated SPECT imagingsession could consume well over six hours in total. Therefore, it wouldbe advantageous to provide a system capable of accurately detectinginfarct areas and ischemic areas of the heart without the need for twoseparate scan sessions performed in conjunction and without theintermediary rest period in between. The present invention offers suchadvantageous capability.

Further, prior art camera systems employing SPECT imaging, in non-gatedperfusion studies, do not offer an advantageous method for detectingfalse positive determinations of an infarct area or an ischemic area ofthe heart. This is the case because other effects, such as attenuationof the radiation signal or statistical variations of the radiationdistribution may create artifacts within the image system that mimicdiseased areas of an image. It is difficult to accurately andefficiently determine whether particular regions of images from thesenon-gated SPECT systems are actually an infarct or ischemic area orrather simply an artifact as a result of one of the above effects. Forexample, a resultant image from a male heart often contains artifacts(false positives) in the inferior heart area as a result of radiationattenuation of the diaphragm, which varies due to the diaphragm size.Also, a resultant image from a female heart often contains artifacts(false positives) in the anterior lateral to anterior septal areas ofthe heart as a result of radiation attenuation from the breasts, whichmay vary due to breast size. In these cases for both males and females,is desirable to be able to detect and correct for these false positives.It would be advantageous to provide an efficient system forquantitatively testing false positive ischemic and infarct areas of theheart. The present invention offers such advantageous functionality.

Gated SPECT camera systems are similar in nature to the non-gated SPECTcamera systems described above, however, the imaging of the object isgated at discrete intervals of time during the cardiac cycle for eachdiscrete angle of rotation of the camera detector. Gated SPECT increasesthe sensitivity and specificity of diagnosis as compared to non-gatedSPECT procedures because gated SPECT allows the observation of bothcharacteristics of perfusion and function within cardiac physiology. Forcardiac gated SPECT camera systems, the timing intervals aresynchronized to different segments of the cardiac cycle. The heartbeatcycle contains locations indicating a systolic phase of the heart wherethe heart tissue is contracting to pump blood and a diastolic phase ofthe heart where the heart is expanding and filling with blood. Bysynchronizing the collection of imaging information from the heart (theobject of interest in cardiac studies) at the diastolic and systolicphases of the cardiac cycle, the gated SPECT camera system can providephysicians with images of the heart during both contraction andexpansion. This information is utilized in diagnosing heart disease,such as CAD. Gated SPECT camera systems can be utilized to image theheart at any timing segment within the heartbeat cycle (cardiac cycle).Typically in gated SPECT techniques, the image of the heart at the endof the diastolic phase (end-diastole) is recorded and studied and theimage of the heart at the end of the systolic phase (end-systole) isrecorded and studied.

According to gated SPECT studies, if a heart region is detected with acertain count density in the myocardium at maximum expansion(end-diastole) and this region does not show much increased countdensity at minimum expansion (end-systole), then the myocardium in thelocation of the defect may be ischemic or artifactual. If the countdensity remains constant over the time segments then the defect mayrepresent an infarct or dead tissue. It would be advantageous to utilizethe above principles in conjunction with wall movement data in a nuclearcamera imaging system to provide quantitative information regarding themyocardium which can be used for diagnosis. The present invention offerssuch capability by providing specialized quantitative displays of thegated SPECT image data.

Prior art systems of gated SPECT nuclear camera systems have focusedprimarily on qualitative studies over quantitative studies. To thisextent, images generated at end-diastole and end-systole have beenpresented to the diagnosing physician without any meaningfulquantitative analysis of the structures or movements of structures ofthe heart. This leaves determination and diagnosis of possible diseasedareas of the heart (i.e. infarct or ischemic areas) to approximate andnon quantitatively based judgments on the part of the physician. Itwould be advantageous to provide a gated SPECT nuclear camera imagingsystem that offered quantitative analysis and measurement display of theheart region or regions under review. This quantitative data could thenmore effectively aid a physician in diagnosing areas of CAD andaccurately reproduce such findings. The present invention offers suchadvantageous quantitative information analysis and display capability.

Other prior art systems determined ejection fractions as an alternateavenue for CAD diagnosis and employ gated SPECT camera systemsqualitatively to determine the ejection fraction. The ejection fractionis the percent of total blood in the heart cavity that is actuallyejected from the heart during contraction and expansion. Gated SPECTtechniques are utilized to image the heart during contraction (systole)and during expansion (diastole) to determine the heart volumes at theseperiods which can be used in diagnosing heart disease to determine theejection fraction. The ejection fraction is determined as a ratiobetween the difference of the volume of the heart at diastole andsystole over the volume of the heart at diastole. A low ejectionfraction may indicate an infarct or ischemic area The above prior artmethods of determining the ejection fraction are limited because thedetermination method of the systolic and diastolic volumes is notaccurate and the determination more often than not is the result ofapproximation and qualitative judgment based on qualitative informationpresented to the physician. Since the volume determinations are notquantitative, the ejection ratios determined are not quantitative andnot readily reproduced lending various contradictory diagnosis for agiven condition. Aside from the qualitative nature of the image data,physical limitations in the camera resolutions and partial volumeeffects severely degrade the accuracy and reproducibility of thedetermination of these two volumes. It would be advantageous to providequantitative method for determining cardiac disease using gated SPECTtechniques over the above prior art design. The present inventionprovides such capability.

Additionally, prior art nuclear camera systems collect data from thecamera detector using two data parsing passes. The first parsing passexamines each byte or word of data that is detected by the cameradetector and is used to construct a temporary histogram for a particularheart beat, this is called a beat histogram. After the first parsingprocessing is complete, a second processes sums the beat histogram datawith the overall or total sum histogram that represents histogram datafor all imaged beats for a given projection angle and for a given gatedsegment. If the newly collected beat histogram represents data from aheartbeat that is to be rejected, then the beat histogram data will beerased and therefore ignored. This prior art process requires a greatdeal of time and processing power because, essentially, the input datafrom the detector must be completely parsed twice before it isincorporated into the summation histogram. Further, if a particularheartbeat is to be ignored, it is wasteful of processing power andinefficient to construct the beat histogram.

Therefore, what is needed is a method of determining bad beats withoutinefficient construction of the beat histogram Further, what is neededis a way to implement the data acquisition processing of the nuclearcamera system that can eliminate the double parsing required if datafrom a bad heartbeat is detected and avoid constructing a beat histogramthat is never used. The present invention provides such capability.Further, the present invention also offers the capability, upondetection of a bad current heartbeat, of skipping the datarepresentative of a just previously imaged heart beat.

Accordingly, it is an object of the present invention to provide anuclear medicine imaging system for aiding in the diagnosis of cardiacdisease using gated SPECT techniques. It is an object of the presentinvention to provide a nuclear medicine imaging system for aiding in thediagnosis of cardiac disease without requiring both a stress imagingsession and a rest imaging session in conjunction. Further, it is anobject of the present invention to provide a gated SPECT imaging systemwherein wall motion and wall perfusion can be quantitatively the heartand rendered with respect to various images of the heart at variousgated segments of the cardiac cycle. It is also an object of the presentinvention to provide a nuclear imaging camera system capable ofeffectively and efficiently detecting false positives for infarct andischemic areas of the heart. It is yet another object of the presentinvention to provide a gated SPECT system for providing a functionalimage that simultaneously displays both wall movement and wallthickening information. It is also an object of the present invention toprovide an effective display system allowing efficient location, displayand comparison of image frames of the multitude of image frames that aremade available from the spatial slices and temporal segments ofreconstructed volumes resultant from a gated SPECT study. It is anobject of the present invention to provide an efficient data acquisitionprocedure of a camera system that has the ability to skip bad beat dataevents without constructing a beat histogram These and various otherobjects not specifically mentioned above will become evident uponfurther review of the discussions of the present invention to follow.

SUMMARY OF THE INVENTION

The present invention includes embodiments covering an apparatus andmethod for acquisition, processing and display of image data from anuclear camera imaging system. The preferred embodiment of the presentinvention utilizes image data originating from a gated SPECT (SinglePhoton Emission Computerized Tomography) nuclear camera system. Thepreferred embodiment of the present invention includes specializeddisplay screens and display formats optimized to display quantitativeinformation regarding two parameters of cardiac physiology: perfusionand function within the same display. This specially optimized screenallows efficient detection of an infarct area as well as an ischemicarea within the cardiac tissue under review. This element of thepreferred embodiment of the present invention provides a physician, ordetermining medical technician, a method and means for analyzing theacquired image data from the nuclear camera system in the diagnosis ofcoronary artery disease (CAD) by creating functional images representingquantitatively computed values for both perfusion and function.

Embodiments of the present invention also include a system forprogramming, saving and recalling a number of default parameters andprotocol that control the data acquisition and processing phases of theimaging procedure. Using such predefined default parameters forprocessing, the imaging system of the present invention can beeffectively and efficiently utilized without time consuming parameteradjustments that might otherwise be required for entry. Furtherembodiments of the present invention include a system and display formatfor efficient and comprehensive display and comparison of imagesrepresenting slices of reconstructed volumes that are reconstructed fromimages acquired by the camera system This display format allows a numberof different images to be easily displayed, referenced, compared, andrecalled within a high resolution color computer display screen usinguser interface mechanisms.

More specifically, embodiments of the present invention include anapparatus for presenting quantitative image information used fordiagnosing heart disease, the quantitative image information based ondata obtained using gated SPECT techniques, the apparatus comprising:means for displaying a first image of a myocardial structure duringdiastolic phase of a cardiac cycle; means for displaying a second imageof the myocardial structure during systolic phase of a cardiac cycle;means for selecting a region of interest of the first image and also forselecting a region of interest of the second image; means for computingperfusion ratios and wall movement factors for individual sections ofthe myocardial structure defined by the regions of interest; and meansfor displaying a functional ring representative of the myocardialstructure, the functional ring comprising representations of both theperfusion ratios and the wall movement factors of the individualsections of the myocardial structure.

Embodiments of the present invention include the above wherein theregion of interest of the first image and the region of interest of thesecond image are each divided into a plurality of individual sectionsand wherein a section pair comprises sections of each region of interestthat correspond to a same portion of the myocardial structure andwherein the means for displaying a functional ring representative of themyocardial structure comprises: means for displaying a plurality of arcsections comprising the functional display ring, wherein each arcsection corresponding to an individual section pair, means for coloringeach arc section depending on a perfusion ratio for the each arcsection; and means for varying radial width of the each arc sectiondepending on a wall movement factor for the each arc section.

Further embodiments of the present invention include a computerimplemented method for displaying information on a display screen usedin diagnosing heart disease, the information obtained using gated SPECTimaging techniques and tomographic reconstruction procedures, the methodcomprising the computer implemented steps of: receiving a plurality ofcomputed ratios representing myocardial perfusion for a selected regionof myocardium; receiving a plurality of computed wall movement factorsrepresenting myocardial wall movement for the selected region ofmyocardium; rendering a functional ring on the display screen comprisinga plurality of arc sections, the plurality of arc sections presentingrepresentations of both the computed perfusion ratios and the computedwall movement factors.

Embodiments of the present invention include the above and furtherwherein the step of rendering a functional ring comprises the steps of:displaying each of the plurality of arc sections with an individualcolor representation based on an individual perfusion ratio of theplurality of myocardial perfusion ratios; and displaying each of theplurality of arc sections with an individual arc section width based onan individual wall movement factor of the plurality of computed wallmovement factors.

Additional embodiments of the present invention include in a nuclearcamera system having an acquisition processor, a memory unit, and atleast one detector unit for detecting image events, a computerimplemented semi-list acquisition method for parsing the image events tocreate, the method comprising the computer implemented steps of:receiving individual data event words for an entire R-R interval to forma current data event word set; storing the data event words in list formfor an entire R-R interval in a buffer of the memory unit; andindicating, within unique locations with the current data event set, astart address for a subsequent data event word set and a count numberrepresentative of the duration of the R-R interval of the current dataevent word set, monitoring the unique locations of the start address andthe counter number until one of the locations contains a non zero value;and binning the data event words for the entire R-R interval directlyinto a summation histogram.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates three main systems of the present invention, thenuclear camera 10, the data acquisition computer 20, and the image dataprocessing (reconstruction) and display system 120.

FIG. 2 illustrates a block diagram of elements of the post dataacquisition processing (reconstruction) and display system 120 of thepresent invention.

FIG. 3 illustrates the parameter selection screen of the dataacquisition system 20 of the present invention.

FIG. 4A illustrates the major processes of the invention and datastructures.

FIG. 4B is a flow diagram illustrating data acquisition procedure andthe major processing blocks of the image processing 400 aspects of thecomputer system 120 of the present invention.

FIG. 5 is illustrates the reconstruction parameter screen of the presentinvention.

FIG. 6 is an illustration of the main processing screen of theprocessing (reconstruction) section of the present invention.

FIG. 7 illustrates the filter screen of the filter processing of thepresent invention allowing filter parameter modification and storage.

FIG. 8 is an illustration of the review screen of the present inventionallowing display of cine SPECT and cine gated images of the raw gatedSPECT data.

FIG. 9A illustrates the major processing blocks of the displayprocessing 900 of the present invention.

FIG. 9B is an illustration of the three datasets (an associatedorientations) created by the reconstruction processing of the presentinvention.

FIG. 10 illustrates the main display screen and related series of shortaxis images and series of vertical and horizontal long axis images ofthe present invention.

FIG. 11 illustrates the 3-D image screen of the display screenprocessing of the present invention.

FIG. 12 is an illustration of the images display screen of the displayscreen processing of the present invention displaying separate series ofimage frames for short axis, vertical long axis and horizontal long axisdatasets.

FIG. 13 illustrates the quantification ("quantify") screen andillustrates selected regions of interest (R01) and associated functionaldisplay rings of the preferred embodiment of the present invention.

FIG. 14 is a detailed illustration of the section arcs that comprise asingle functional display ring of the preferred embodiment of thepresent invention to illustrate wall motion thickness dimension andperfusion ratio color coding.

FIG. 15 is an illustration of the flow processes 1510 of the presentinvention used for rendering the various functional display rings of thequantify screen processing 940 of the preferred embodiment of thepresent invention.

FIG. 16 illustrates the graph screen of the display processing of thepresent invention for numeric representation of computed perfusionratios.

FIG. 17A is a representation of the major processing steps of thesemi-list mode acquisition procedure of the present invention.

FIG. 17B is a representation of the data structure of the event words ofR-R intervals stored within the ring buffer of the present invention.

FIG. 17C is a flow diagram of the major processing blocks of the firstand second processes of the semi-list mode acquisition procedure of thepresent invention.

FIG. 18 is a flow diagram of the steps of the binning process of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the present invention numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be obvious toone skilled in the art that the present invention may be practicedwithout these specific details. In other instances well known methods,components, processes, and systems have not been described in detail asnot to unnecessarily obscure aspects of the present invention. Someportions of the detailed descriptions which follow are presented interms of algorithms and symbolic representations of operations on databits within a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the dataprocessing arts to most effectively convey the substance of their workto others skilled in the art. Unless specifically stated otherwise asapparent from the following discussions, it is appreciated thatthroughout the present invention, discussions utilizing terms such as"processing" or "computing" or "calculating" or "determining" or"displaying" or the like, refer to the action and processes of acomputer system, or similar electronic computing device, thatmanipulates and transforms data represented as physical (electronic)quantities within the computer system's registers and memories intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices.

Introduction

The following detailed discussion is segmented into five major sectionsfollowing this introduction. Section I covers the overall components ofthe individual systems of the present invention including FIGS. 1-2,section 11 covers the image acquisition system and procedures includingFIGS. 3-4, section III covers the processing procedures including FIGS.5-8 and section IV covers the image display procedures including FIGS.9-16.

The data acquisition system of section II is primarily composed ofcamera system and computer and gathers raw gSPECT image data. A computerprocessing system of section III then takes the raw gSPECT image dataand reconstructs the data into three individual datasets each composedof a series of image frames representative of reconstructed volumes ofthe raw gSPECT image data. Section IV covers an image display systemthat allows visualization of these image frames and also allowsquantitative and qualitative analysis of the image data including asegmented functional display illustrating perfusion ratios and wallmovement for a selected section of myocardium. The image display systemof section IV is used as a tool for physicians in diagnosing cardiacdisease. Section V covers aspects of the present invention that areimplemented within camera system 10 of the present invention to improvethroughput and processing efficiency of the image data received from thedetector 12 and passed to the data acquisition computer 20 byimplementing a semi-list mode acquisition procedure. The followingintroduction describes major aspects of the present invention.

A basic premise of the present invention is to utilize the image displayprocessing (section IV) to provide meaningful quantitative measurementand display of two valuable pieces of information that are collected andavailable using gated SPECT imaging: wall motion and wall perfusion ofthe myocardium to enable accurate diagnosis of CAD. Gated SPECT camerasystems collect images from a patent, in a single imaging session, thatcontain information of the heart (1) at rest for wall motion and (2) atstress for blood perfusion. For instance, gated SPECT camera systemsimage the heart during an interval where the patient is still which isdefined as a rest condition. Even if the heart was exercised a fewminutes prior to imaging, the heart enters and remains in the restcondition by the time the imaging process or session begins. The gatedSPECT system collects images of the heart at different time periods(segments) of the cardiac cycle as the heart is in motion and thisinformation is used by the present invention in part to compute anddisplay wall motion information. Therefore, wall motion informationrepresents the heart during the rest condition. However, theradionuclide used for imaging is introduced into the blood during astress condition and distributes in the heart at stress. Throughout thegated SPECT imaging session, the radionuclide will remain in this stressdistribution until metabolized from the heart much later. Therefore,although the heart enters the rest condition during imaging (asdiscussed above) the radionuclide distribution remains in the samedistribution as introduced in the stress condition.

The present invention advantageously utilizes the above rest/stressimage data to display, quantitatively on a single functional displayring, images of the heart at stress (perfusion) and images of the heartat rest (wall motion) for diagnosis using only one imaging session. Tothis extent, a displayed structure of the myocardium on a display screenis segmented into regional areas by a computer and the counts in theregional areas can be measured at end-diastole (ED) and end-systole (ES)segments of the cardiac cycle. The total counts within these regionalareas (sections) remain approximately the same at ED and ES, however,the average maximum pixel count density increases at ES for a healthyheart as compared to the similar regional area for ED. This is becausethe myocardium is at contraction during end-systole and more of theradionuclide is concentrated per sectional area during end-systole ascompared to end-diastole when the heart is expanded and filling withblood.

One aspect of the present invention creates specialized functionaldisplay rings on a color computer display screen to quantitativelyrepresent perfusion and function in conjunction with respect to eachcorresponding sectional area for ED and ES image segments. According toa method of the present invention, regions of interest are selected withrespect to two images, an end-diastole image and its associatedend-systole image which are both displayed on the computer screen at thesame time. The user applies a separate circular region of interest (ROI)which is divided into 8 (or 16) pie shaped sub-region, or sections oneach image of the ES/ED pair. The center and diameter of the region ofinterest (and thus the area of any particular section) are useradjustable with respect to associated images of the myocardium at enddiastole and end-systole. The aspects of the functional image of thepresent invention that relate to perfusion are based on dividing themaximum pixel value (i.e., the count value of the pixel having themaximum count) at ED by the maximum pixel value at end-diastole. If thesegmented myocardium is normal then the ratio should be greater then 1.0as discussed above (i.e., more dense at end-systole). With respect towall movement, the maximum pixel values at ED and ES are used to computea center of mass for each section by dividing the total number of pixelsin the section by the total counts in the section for all pixels. Aradial distance is then computed from the center of mass of the sectionto the center of the region of interest for ED and ES. A displacementfactor is computed by the present invention which represents the changein radial distances between the ED section and the associated ESsection. The computed width of the functional display section may benegative or positive depending on displacement in the corresponding ROI.The above must be done by the present invention for each section of thecorresponding ROIs for ED and ES.

Specifically, with regard to the display format, the present inventionprovides a separate functional display arc section for each section pair(ES/ED) and displays the ratio for each section pair by color coding thearc section and spatially locates the arc within the ring in thefunctional display ring according to the spatial location for theparticular section pair. The width of each arc is determined by the wallmovement value for each section pair. The different colors currentlyutilized by the present invention for perfusion color coding are black,purple, blue, green, yellow, orange, red, and white to represent therange from just less than 1.0 and just greater than 2.0 in 0.1increments. However, any color combination or ratio range capable ofimparting ratio information will suffice within the scope and spirit ofthe present invention including different shades of the same color fordifferent ratio values. The color coded arcs are arranged and applied toform a ring representing the myocardium for a given and selected ROI ofa given tomographic slice, usually of the short axis dataset whichillustrates a circular cross section of the ventricle. Displayinformation is added to the ring to indicate wall motion information(function) between ED and ES segments. This displacement factor isapplied to adjust the width of each color coded arc based on thedisplacement factor for a given ES/ED section pair. The result is afunctional ring color coded to represent wall thickening and varying arcwidths to represent wall motion for associated section pairs of a givenpair of ED and ES ROIs; all within a single display. This process isapplied on a frame by frame basis to a set of frames displayed on thecomputer screen. The systems and procedures of the present inventionwill now be described in more depth.

SECTION I--OVERALL COMPONENT OF THE PRESENT INVENTION

FIG. 1 illustrates the major components of the nuclear camera imageacquisition, processing and display system of the present invention. Thepresent invention includes either a single head (detector) camera or adual head camera 10 (as shown in FIG. 1 a single head camera ispresent). The preferred embodiment of the present invention utilizes aCirrus™ Nuclear Imaging Camera system available from ADAC Laboratoriesof Milpitas, Calif. The Cirrus Camera system is a SPECT camera ideal forcardiac studies and implements gated SPECT imaging techniques.Embodiments of the present invention utilizing dual head camera designsare implemented with the Dual Head Genesys™ Nuclear Imaging system andthe Genesys Vertex™ Camera system also available from ADAC Laboratoriesof Milpitas, Calif. The Genesys™ camera system also supports gated SPECTacquisition. Two arms 11 and 9 mounted on vertical tracks 16 and 15 forma gantry structure that can move the detector head 12 in variousprojection angles to accomplish the required 180 and 360 degreemovements of the detector 12 used in gated SPECT studies. Pivotstructure 17 allows the camera detector 12 and gantry structure to pivotclockwise or counterclockwise. The camera system 10 of the presentinvention includes a detector head 12 comprising a number of well knownradiation detection components of the Anger camera type including aphotomultiplier array, a collimator, a scintillating crystal and adigital pixel output. The camera system 10, in a well known fashion,images the patient to provide digital image data which is binnedaccording to particular discrete angles of rotation in which thedetector 12 traverses about the patient and binned according toparticular segments within the cardiac R-R interval (defined below). Foreach angle of rotation, several segments may be collected of the cardiaccycle. Particular (x,y) coordinate positions within the imaging detectorof the camera system are called pixels and the number of scintillationsdetected by each pixel location is represented by a count value for thatpixel. The resulting digital image data from the camera system 10 isbinned according to the particular discrete angle of rotation in whichthe detector was situated when the image was acquired. Also binned isthe gated segment within the R-R interval in which the data was acquiredin gated SPECT studies. Particular coordinate positions within theimaging detector of the camera system are called pixels. Each pixelcontains a count value representing the number of radiation emissionsdetected at that location of the detector 12. The pixel matrix of (x, y)locations is referred to herein as a histogram of scintillations atthese coordinate locations. It is understood that a histogram representsa raw image. For example, a typical detector 12 may have resolution of(64×64) pixels or (128×128) pixels available for imaging for modes ofthe invention and is capable of imaging at approximately (1000×1000)resolution maximum Within each pixel location reported by the camerasystem 10, is a scintillation count number for that pixel.

The camera system 10 is coupled to a data acquisition computer system20, which in the present invention is implemented using a generalpurpose computer system having high speed communications ports for inputand output coupled to a two way data transmission line 19 which couplesthe camera system 10 to the computer system 20. The computer system 20communicates data acquisition parameters (also called data acquisitionprotocols) selected by a user to the camera system 10 to initiate aparticular type of gated SPECT study within the camera system 10. Theimaging data from the camera system 10 is then transferred over line 19to the communications device of the system 20 and such raw gated SPECTimage data is then forwarded to a post acquisition processing computersystem 120. The data acquisition system 20 also comprises a keyboardentry device 21 for user interface to allow selection and modificationof predefined data acquisition parameters which control the imagingprocesses of the camera system 10. Also coupled to the data acquisitionsystem 20 is a standard color display monitor 20 for display ofparameter information and relevant information regarding the particulargated SPECT study underway (such as imaging status communicated from thecamera system 10 during an imaging session).

A cardiac electrode and signal amplification unit 25 is also coupled tothe data acquisition computer system 20. This unit 25 is speciallyadapted to couple with a patient's chest near the heart to receive theheartbeat electrical signal. This electrode unit 25 is composed of wellknown heartbeat detection and amplification techniques and componentsand any of several well known devices can be utilized within the scopeof the present invention. In order to perform gated SPECT analysis onthe heart, the heartbeat pulse or electrical wave must be studied foreach patient, as each heart is different. The heartbeat wave is examinedto determine the points within the cycle where the well known R wave isencountered. The time interval between successive R waves is measured bythe present invention to determine the R-R interval. These points andtiming intervals between these points will be used to gate the imagingprocess of the camera system 10 during the cardiac cycle andparticularly at the end-diastole and end-systole interval segments. Thepreferred embodiment of the present invention automatically, undercontrol the system 20, collects five sample heartbeat waves once thedetector 25 is located on the subject patient in order to determine theaverage R-R period. This information is fed to the computer system 20and then sent to the camera system 10, however such information couldalso be detected and determined directly by the computer system 10 oncequeued to do so by the acquisition computer system 20 under usercontrol. For a particular projection angle, the system 10 then directsthe acquired imaging counts to the first segment bin, and upon eachsuccessive time interval the image data is directed to a new gated bin.When the R wave is detected once more the first bin receives the imagedata again and the process continues through each other segment andassociated bin until a new projection angle is encountered. Theelectrode 25 also is used by the camera system 10 in order to detect thestart of a cardiac cycle and gate the camera imaging systemappropriately depending on the number of selected segments of the R-Rinterval for collection.

As discussed above, the data acquisition phase of the present inventionimaging system is composed of camera system 10 and computer system 20.Referring still to FIG. 1, the image data is sent from the camera system10 over line 19 to acquisition system 20 and then over line 22 to theimage processing system 120. This system 120 is responsible todisplaying and quantifying certain data acquired by system 10 and system20. Specifically, according to the present invention, this system 120will process and uniquely display quantitative information regardingblood flow within the myocardium (perfusion) and wall motion of themyocardium (function) as a result of the gated SPECT data acquired.

Post Data Acquisition Processor System 120. The Post Data AcquisitionProcessor System 120 acquires the raw gated SPECT image data generatedfrom the camera system 10 and using user configurable procedures,reconstructs (performs tomography or back projects) the data to providea reconstructed volume and from the volume generates specialized imagesof the myocardium for diagnosis, including generating and displaying thefunctional images as described above. The generated images or frames ofthe myocardium represent different slices of the reconstructed volumeheart at variable thickness in a short axis dimension, a verticaldimension and a horizontal dimension (all three are user configurable)for a number of gated time segments. Therefore, complete threedimensional information can be displayed by display 105 in a twodimensional manner in a variety of formats and orientations by thepresent invention including a display providing quantitative informationregarding both wall thickening perfusion) and wall motion (function) ofthe myocardium under study.

The computer system 120, illustrated in FIG. 2, is a SPARC systemavailable from Sun Microsystems of California as modified with a Pegasyshardware backplane available from ADAC Laboratories, however any numberof similar computer systems having the requite processing power anddisplay capabilities will suffice within the scope of the presentinvention. Generally, the computer system 120 comprises a bus 100 forcommunicating information, a central processor 101 coupled with the busfor processing information (such as image data and acquired counts) andcommand instructions, a random access memory 102 coupled with the bus100 for storing information and instructions for the central processor101, a read only memory 103 coupled with the bus 100 for storing staticinformation and command instructions for the processor 101, a datastorage device 104 such as a magnetic disk or optical and disk drivecoupled with the bus 100 for storing information (such as image databoth raw gated SPECT and reconstructed data sets.) and commandinstructions, and a display device 105 coupled to the bus 100 fordisplaying information to the computer user. There is also analphanumeric input device 106 including alphanumeric and function keyscoupled to the bus 100 for communicating information and commandselections to the central processor 101, a cursor control device 107coupled to the bus for communicating user input information and commandselections to the central processor 101 based on hand movement, and aninput and output device 108 coupled to the bus 100 for communicatinginformation to and from the computer system 120. The signal generationdevice 108 includes, as an input device, a high speed communication portconfigured to receive image data acquired by the nuclear camera system10 and fed over line 22.

The display device 105 utilized with the computer system and the presentinvention may be a liquid crystal device, cathode ray tube, or otherdisplay device suitable for creating graphic images and alphanumericcharacters recognizable to the user. The display unit 105 of thepreferred embodiment of the present invention is a high resolution colormonitor. The cursor control device 107 allows the computer user todynamically signal the two dimensional movement of a visible symbol orcursor 5 (pointer) on a display screen of the display device 105. Manyimplementations of the cursor control device are known in the artincluding a trackball, mouse, joystick or special keys on thealphanumeric input device 105 capable of signaling movement of a givendirection or manner of displacement. It is to be appreciated that thecursor means 107 also may be directed and/or activated via input fromthe keyboard using special keys and key sequence commands. In thediscussions regarding cursor movement and/or activation within thepreferred embodiment, it is to be assumed that the input cursordirecting device may consist any of those described above andspecifically is not limited to the mouse cursor device. It isappreciated that the computer chassis 110 may include the followingcomponents of the present invention: the processor 101, the ROM 103, theRAM 102, the data storage device 104, and the signal input and outputcommunication device 108 and optionally a hard copy printing device.

SECTION II--Data Acquisition Procedures of the Present Invention

The data acquisition system 20 (FIG. 1) allows a user via keyboardcontrol to select and/or create a predefined set of parameters (orprotocol) for direction of a gated SPECT imaging session by the camerasystem 10. FIG. 3 illustrates a parameter interface screen andconfigurable parameters of the present invention for data acquisitionthat are selected and displayed on screen by the user via keyboard 21.The following are descriptions of the parameters configurable by thepresent invention data acquisition system 20. It is appreciated thatonce set, the following parameters can be saved and referenced in acomputer file for subsequent recall. This parameter or protocol file canbe then recalled and utilized for a particular gated SPECT study thuseliminating the need to enter again the parameters for similar oridentical gated SPECT studies. The parameter file name as shown in FIG.3 is "GATED SPECT" and is indicated at 300. It is appreciated that thecomputer system 20, once instructed by the user, will relay theparameters set by the user to the camera system 10 in order toinitialize and begin a particular gated SPECT study. The initiation isdone by selection of menu 357.

Refer to FIG. 3. The present invention data acquisition system 20 allowsthe user to select the total orbit of the camera detector 12 for thegated SPECT study or for a regular SPECT study at 180 degrees or fullcircle 360 degrees. If 360 degrees total orbit are selected, the maximumnumber of projection positions available are 128 or 2.81 degrees perprojection and the minimum number of projection positions is 32representing 11.25 degrees per projection. Selection for number ifprojection angles during the total orbit (i.e., number of ECT frames togather during the total orbit) is entered via 303 and is either 64, or128. The maximum pixel matrix size for the detector 12 imaging surfaceis 128×128 pixels and entry is by selection 305. The starting projectionangle of the detector 12 is selected as any angle within 360 degrees atselection 307. The direction of rotation for the detector 12, eitherclockwise or counter clockwise may be selected by a parameter of thepresent invention at selection 309. The patient orientation may also beselected by the computer 20 as: feet in face up, feet in face down, headin face up, or head in face down at selection 311. The patientorientation may also be specified by a selection for supine or prone at311. It is appreciated that the present invention allows selection ofthe total time per ECT projection by allowing the user to set the totaltime per projection angle or the number of beats per projection angle at343.

The duration of time spent at each rotation angle is held constant bythe present invention by time normalization of the good beats. Accordingto the normalization procedure, the total time of good beats imaged ateach rotation angle is held constant and the imaging time for each ofthe gated segments is held constant. According to this normalizationprocedure, count numbers, based on count number and averages, are addedto deficient imaging bins in order to increase the count number fornormalization purposes on a proportionate basis. The present inventionallows for parameter set up for the particular orbit utilized by thecamera system, i.e., if selected circular then the user must optimizethe collimator to patient distance; which is selected at input 313.Selection is also provided to allow the patient to collimator distanceto be automatically computed and controlled. The computer system 20 alsoallows for flood correction parameter configuration which allows theuser to select the flood correction matrix for correctingnon-uniformities associated with the scintillation detectors 12 at input315. The correction will be applied on the post data acquisition system120 as the image data for each projection angle is stored within system120.

Refer to FIG. 3. The present invention allows for selection of eithercontinuous imaging or step and shoot data acquisition via an inputcalled acquisition method at 317. Both methods are well known in theart. The present invention allows for selection of either continuousimaging or step and shoot data acquisition via an input calledacquisition method at 317. Under continuous acquisition, the camerasystem 10 will acquire image data during the translation phase from oneprojection angle to the next to increase acquisition of image data andimprove image quality. The data will be acquired in frame mode, but aframe of data (a projection) will include acquired data at thedetermined angle plus the acquired data during the movement of thedetector to the next location. In order for each projection to containthe same amount of acquisition time, the last frame acquired mustinclude data from the static location and the data during thetranslation period to the next static location. If during thetranslation an R-R interval is detected that is outside an allowablerange (see below), this beat will be rejected by the present inventionbut the acquisition time will not be extended. The translation willcontinue to the next angle for imaging. The time normalization processof the present invention will compensate for the difference in totaltime acquired at the end of the imaging session. During step and shootSPECT acquisition, the camera system 10 does not acquire image dataduring the translation phase from projection angle to projection angle.It is appreciated that if the time to translation to a new projectionangle occurs during an acquisition of an R-R interval, the for thatinterval is allowed to complete before the translation action is takenby the camera system 10.

The following discussion and parameter configurations are relevant togated SPECT studies. The acquisition computer 20 allows the user toconfigure the maximum number of gated segments per R-R interval aseither 8 or 16 at input 331. Therefore, if the mean R-R interval wasoriginally computed as 800milliseconds and 16 segments were selected,then each gated segment would represent 50 milliseconds of the R-Rinterval. The present invention also allows the user to select thetriggering factor to terminate a particular projection, either the totaltime per projection, or a set number of detected R-R intervals. Imagedata from several R-R intervals is taken per projection angle. This isselected at 343. The user may also select R-R interval variance byentering a maximum percent window variance (100%) at 333 and a minimumpercent window variance (0%) at 335. The user may also selection anumber of good R-R intervals to exclude after a variance outside theabove window is detected at input 341. The user may select a fixed R-Rinterval in the event an automatic R-R interval is not desired at input337. The user may also allow the R-R interval to be recomputed duringthe study based on the average of all beats from the previousprojection. Session information is also displayed such as the isotope IDmay be entered at 351 as well as the patient ID at 353 and theparticular view ID at input 355. Imaging of the camera system 10 isinitiated by an input selection 357.

As shown above, the present invention allows user configuration ofparameter that relate to the R-R interval of the patient heartbeat whichis the interval between successive R waves of the heartbeat wave. Eachframe of the gathered gated SPECT data will be a gated datasetrepresenting a segment of the R-R interval of the heartbeat. In theautomatic mode (selection 339=0), the time per segment of this gateddataset is established by the data acquisition computer 20 or by thecamera system 10 based on the number of dynamic segments selected by theuser (8 or 16) by input 331 and the patient's R-R interval as determinedor as input via 337. The data acquisition computer 20 or the camerasystem 10 (via the electrode 25 of FIG. 1) monitors five of thepatient's R-R intervals to establish the total cardiac cycle time. Thisacquisition computer will establish the time per segment to acquire thedynamic dataset based on the number of segments selected by the user(i.e., 8 or 16 between an R-R interval). The segments will represent100% of the cardiac cycle.

The computer system 20 of the present invention also allows theconfiguration of acceptable R-R interval variations which are used toestablish determination of acceptable and unacceptable heartbeats forimaging purposes. The user may select a timing window around thepatient's R-R interval to accept a percent of variance allowed for eachR-R interval acquired. This window (see inputs 333 and 335) willencompass a variance from 0 to 100 percent Also, as a result of aparticular variance outside the allowed scope, the camera system 10 isprogrammed to skip a certain amount of succeeding beats. The user maydetermine the number of R-R intervals to reject after a variance that isoutside the allowable window, see input 341. This number of rejected R-Rintervals is programmable. Using a fixed R-R interval parameterselection, the R-R interval will be divided by the originallyestablished time per gated segment, in other words, each segment have atime period of the R-R interval divided by either 8 or 16 depending onthe user selection.

For a given projection angle when variable R-R intervals (selected byinput 339) are selected, the mean R-R interval used in the previousprojection angle acquisition will be used as the R-R interval for thenext projection angle acquisition. This means that the R-R millisecondvalue and the value for each binned gated segment, established at thestart of the study, can vary throughout the study. The number of gatedsegments (i.e., 8 or 16) will stay the same and the data will be binnedin the same memory location and the R-R percent variance will remain thesame. It is appreciated that the above allows the user to continue theacquisition even if the patent's R-R interval changes during the study.

During a gated SPECT session of the present invention, the camera system10 periodically communicates with the acquisition computer system 20 torelay certain status information that is displayed on the display screenof computer system 20 (shown in FIG. 3 in status window 365). Forinstance, the current session time is transferred and displayed bycomputer system 20 as well as the current projection and the maximumnumber of frames selected in the gated SPECT study. Also sent to thecomputer system 20 are the current number of counts per second detectedby the detector 12 and the heartbeats detected by the camera system 10.Also reported to the system 20 is the current value of the average R-Rinterval determined by the camera system 10 and the number of gatedframes selected for the study. Also relayed is the status of the maximumnumber of gated frames selected by the user. This status is periodicallytransferred to the system 20 and displayed on the computer screenthroughout the gated SPECT study for monitoring by the user.

Once the above discussed parameters are selected by the user they may bestored within computer system 20 for later recall and use. It isappreciated that once input, the data acquisition computer willinitialize a gated SPECT study on the camera system 10. It is furtherappreciated that the camera system 10 will supply imaging data to thepost acquisition computer system 120. The image data transferred fromthe data acquisition systems to the post acquisition processor 120 is inthe following format viewed in a matrix form but stored as a singleobject. Down the vertical axis is each gated time interval (segment) ofthe cardiac cycle (there can be up to 16 of these segments). Across thehorizontal are the number of projection angles or frames that can betaken over the total orbit selected (there can be up to 128 of these).Therefore, in a standard gated SPECT session there can be up to 128×16or 2048 different image frames of raw gSPECT data. Also, each separateimage frame may be composed of 128×128 pixels maximum, each pixelrepresenting the number of counts received at that pixel location.Therefore, the maximum data size for the raw data of a gated SPECTsession is 2048×128×128 or 33.6 Megabytes of image information. As asingle object, the post acquisition computer may display the data ineither of two formats: (1) cine (animate) the data in gated fashion perprojection angle or (2) cine all projection images for a gated segment.

According to the overall sequences of data acquisition, processing anddisplay of the present invention, a patient is first exercised to stressthe cardiac tissues (using a treadmill or bicycle for instance). Aradio-pharmaceutical is introduced into the myocardium while it isstressed and follows the blood flow to concentrate in areas of thestressed myocardium. During the imaging session, this radionuclide willremain in these areas, even after the heart enters a rest condition (asis well known). At some point the electrode 25 (a standard 3 or 4 leadECG placement) is positioned over the chest near the heart at a positionto best detect and amplify the electrical signal generated by thebeating of the heart and the computer system 20 computes an average R-Rinterval. The patient is positioned in the camera system 10 and aselected data acquisition parameter file is selected entered or modifiedby user control over the data acquisition computer 20. Next, a gatedSPECT imaging session is started on the camera system 10 and operatesaccording to the elected operating parameters supplied by the dataacquisition computer system 20. It is appreciated that once initialized,except for some status reporting from the camera system 10 to the dataacquisition computer system 20, the camera system 10 is independent andperforms the required projection angle motion of the detector 12,gating, and imaging without interface with the computer system 20. Allraw gated SPECT image data is sent to the post data acquisitionprocessing system 120 via lines 19, 22 and the communications interface(intermediary) in the system 20.

The image processing and display procedures of the present invention areimplemented on the post acquisition computer system and will be furtherexplained below in section III. The post acquisition processing computer120 performs three major processing steps: (1) processing orreconstruction procedures; (2) image display procedures; and (3)quantitative analysis procedures (a division of the image displayprocedures) which utilize the functional display rings of the presentinvention. Each of the three above processing tasks of the preferredembodiment of the present invention include user interface capability(via keyboard 106, cursor control 107 and display unit 105) and will befurther explained in discussions to follow.

FIG. 4A illustrates the overall flow of the gSPECT acquisition 20, thegSPECT processing 400, and the gSPECT display 900 blocks including thedata structures 465,470 that are passed to each process. The gSPECTacquisition 20 system delivers to the reconstruction processing 400 araw gSPECT data structure 465 which is composed of raw gSPECT data foreach projection angle of the session, as illustrated by FIG. 4A. Each ofthe individual projection angle datasets is also composed individuallyof segment datasets for each segment of the cardiac cycle selected forimaging. It is appreciated that the data structure 465 could also beorganized first by selected segment and then individually by eachprojection angle, either fashion is within the present invention. ThegSPECT reconstruction processing 400 generates, from the raw gSPECT datastructure 465, reconstructed volume image frames within a data structure470 and passes them to block 900. Structure 470 is composed of a mainheader field indicating the environment of the session, such as patientID, date, hospital, camera name and type, isotope used, calibrationfactors, data sizes, etc. The next sections of the structure 470 are thesegment pointers. Pointers 475a indicate the locations of the threedatasets (short axis, SA, vertical long axis, VL, and horizontal longaxis, HL) for the first selected segment. Pointers 475b and 475cindicate the starting locations for the datasets corresponding to thesecond and n cardiac interval segments, respectively. Each of thesedatasets is composed of oblique image frames of a reconstructed volume.Data structure 470 is saved into memory 102 of the reconstruction anddisplay computer system 120. The display processes 900 make use of thedata structure 470. Generally, at least the ES and ED segments are foundwithin 470.

The data structure 470 also contains a dataset series for the transaxialdataset. Since the transaxial dataset is not pertinent for displaypurposes it is not illustrated in detail.

SECTION III--Processing Procedures and Related Screen Displays onDisplay 105

With reference to FIG. 4B, the overall procedures of the processingaspects 400 of the present invention are represented by a functionalflow chart. The acquired data from step 405 represents the procedures ofthe data acquisition systems of the present invention including thecamera system 10, and the data acquisition computer system 20. Imagingdata originally sent from the camera system 10 is input to the computersystem 120 by processing block 405 and stored in a data storage area 104(of FIG. 2) at step 410. The raw gated SPECT data or raw "gSPECT" imagedata is reported as pixel sets for each projection angle and gatedsegment interval; pixel data being in Cartesian coordinates andrepresenting counts detected at that particular location. The datastorage step 410 also stores the image data in a particular file thatcan be recalled and placed into the computer memory 102 for display andprocessing using predefined patient identification (as discussed above).Once the image data has been received and stored into the computersystem 120 for an entire session, at step 415, the computer system 120allows the user to input a particular patient file for use. The datarepresentative of the selected patient identification is thentransferred from the data store to the processing procedures via 412.

At step 420, the user may modify or add particular parameters thatcontrol the reconstruction processing (i.e., tomography processing) ofthe present invention. Once the parameters are defined at step 425 theymay be saved to create a new parameter file or a previously defined setof parameters may be selected for use. Once the reconstructionparameters are set up, the user may enter a processing block 435 thatgenerates a process screen. The process screen of the present inventionallows selection of particular frames (referenced by pixel locations) ofthe raw gated SPECT data This procedure also allows reconstructionreview options and reorientation capability to properly align the heartfor accepted image display orientations. There are volumetricdeterminations allowed at step 435 and at this step the presentinvention allows selection to the final processing steps 450 where theraw gSPECT data or SPECT data is reconstructed using tomography fordisplay using the data storage device 104 as well as memory 102 forimage data storage. It is appreciated that once the raw gSPECT data isreconstructed, it may be saved back to the disk storage 104 via step 410as a result of flow 414 from the process screen 435.

At block 450 the actual tomography (back projection method) processingof the present invention is accomplished in which the raw gSPECT datacollected at discrete projection angles is transformed computationallyto create volumetric information of the myocardium that can be displayedby a variety of methods at a number of different "slice" positionsthrough the cardiac tissue. The computer processor 101 may perform thesecomputations in a set of parallel processes. As shown in FIG. 4B thereare 16 separate processes that operate in parallel (only four are shownfor clarity 450a to 450d). It is appreciated that according to thepresent invention, these separate processes 450a-450d are machineindependent and may be executed in parallel on multiple machines.According to the preferred embodiment of the present invention theseprocess tasks 450a-450d are performed by the computer system 120. Eachof the 16 processes may operate on a different segment of the raw gatedSPECT image data. It is appreciated that after the tomography processingstep 450 is complete the present invention instructs the computer system120 to the display process 900.

From the processing screen procedures 435, the present invention allowsmodification of particular filters that are utilized in the processes ofblock 450. These filters may be updated and selected at filterprocessing block 430 which generates a filter screen. Processing isdirected from block 435 to block 430 by selection of a filter selectionfield. Processing is returned to the main processing block 430 byactivation of a proceed selection field 710 (see FIG. 7). The presentinvention may also direct the computer system 120 from the mainprocessing screen to processing procedures 440 that generate a reviewscreen (via selection of a review selection field) where SPECT data andgated SPECT data may be displayed and gated. Processing may the returnto block 435 by activation of a cancel selection field 840 (not shown inFIG. 4B) firm the review screen. It is appreciated that normal SPECTdata may be created from the gated SPECT data received at step 405. Thisis accomplished by summing all the gated segment data for a particulardiscrete projection angle and then performing the reconstructionprocesses on this summed data. It is appreciated that the presentinvention allows such functionality at step 440 where both normal SPECTdata and the gated SPECT data image frames may be displayed together forcomparison. This is advantageous due to the familiarity and establisheddiagnostic value of the normal SPECT imaging data. Also at processingblock 440, the present invention allows review of selected raw datapixels of the frames of the gated SPECT study and allows selection ofwhich image data (presented as pixel ranges or volume limits) to processthrough block 450.

Therefore, there are four major process procedures and associatedscreens of the processing tasks of the present invention. They are: theparameter screen, the processing screen, the filter screen, and thereview screen. These screens and related processing tasks of thecomputer system 120 will be discussed further below.

Parameter Screen and Processing 420. The parameter screen 420 of thepresent invention is described further with reference to FIG. 5. Theparameter screen is the entry point for the processing procedures of thepresent invention. All values of the fields shown in FIG. 5 may bestored as default values for predefined processing sequences. The screenselection item (icon) 561 allows the process flow to enter theprocessing of block 425 to define and save default selections. The entryof selection 563 transfers processing to block 435, the process screen.From the parameter screen a default screen may be selected The defaultscreen is important because the entered parameters that were selected bythe user may be stored for later use in a processing default andrecalled automatically. In the default screen (not shown), the user cancreate and name a new processing default set. Also selectable is afunction that will list the previously predefined processing defaultsets. Once created, defined default sets may be stored to and recalledfrom disk 104. The user may highlight a predefined default set and thestored parameters will fill the options on the screen of FIG. 5. Allfields may be edited by the user and range checking occurs for eachfield.

The user may select the icon 535 and enter the patient name, a patientidentification and the date of the particular study under review; theseselections may be done in a pop up screen input (not shown). Under theprocessing defaults, the user may select either qualitative orquantitative method at selection 510 using a cycle entry. A cycle entryis a selection list that cycles through the options of the list eachtime the field is selected by positioning the cursor 5 with the mouse107 and activating a button located on the mouse 107.

Selection 510 cycles through: quantitative; qualitative; and both. Inquantitative mode, the computer system 120 will perform image summationand the output dataset (series of image frames for a selected viewingorientation) will be independently stored in 104. Image summation sumsthe 8 or 16 gated segments for each angle of projection (i.e., itcreates a regular SPECT study). A set of reconstructed images based onthe save objects (540) selections from these summed image sets will thenbe created using the filtration, azimuth and elevation parameters thatcan be defined by the user (see below). The same values designated bythe user on the default screen will be applied to the dataset at thetime of any data save function. In qualitative mode the computer system120 will generate a dataset based on the user defined parameters of FIG.5 but will not create the summed image dataset (i.e., a gated SPECTanalysis is done). In the quantitative/qualitative ("both") mode, bothtypes of summed and not summed datasets are used based on the userdefined parameters.

FIG. 5 also illustrates parameter selections of the present inventionthat relate to filter configurations used in the reconstructionprocesses 450. At this screen, the displayed filter parameters are thedefault values presented by the computer system 120. The filterconfiguration is applied to the gated SPECT data to enhance the dataaccording to the selected parameters. The axis of rotation may bealtered via 526. The frequency cutoff value can be entered via input 527and the order of the filter can be input via 528. The ranges for thecutoff and order are controlled by the type of filter selected. The usercan override these values by going to the filter parameters screen andselecting new values. The last values selected are used by thereconstruction process 450. The filter selected for use is entered via acycle field 520 which cycles through the selections: Butterworth,Guassian, Hamming, Hanning, Wiener, Parzan and Ramp. All of these wellknown filters are available for use by the computer system 120 and eachof the above effect the X-axis (frequency) filtering. As shown, theButterworth filter is selected. The Y-axis filter (amplitude) also maybe altered via cycle field 525 which cycles through smoothing oranalytic. When selected as analytic the Y-axis filter will adopt theparameters set for the X-axis filter. If smoothing is selected theY-axis filter performs a well known smoothing function.

The user interface of FIG. 5 allows the user to input tomographicalreconstruction limits at 529 which represents the pixel range used forreconstruction. This screen allows the user to estimate thereconstruction range in order to insure enough disk space is availablein 104 for the total reconstruction. The user can set the volumereconstruction limits at 529 for a start and end value. These parametersare also adjustable in the processing screen (discussed below). It isappreciated that once these limits are set in the processing screen,they are used to define the volume for all frame reconstruction. Theuser interface of FIG. 5 also allows the user to input reconstructionparameters. The reconstruction (tomography processing) of the presentinvention will produce a three dimensional rendition of the imaged dataand will slice that image in order to display dataset frames of threeviews, the short axis view (reoriented transverse), the horizontal view(coronal) and the vertical long axis view (sagittal). The pixel size ofeach slice of the reconstructed data is determined by the slicethickness (measured in pixels) entered at 512 via a cycle region. Thecardiac orientation is input via 514. It is appreciated that the wellknown American College of Cardiology or "ACC" orientation may beselected according to the present invention.

The transaxial reconstruction of process 450 will be accomplished byreconstructing from the heart apex to the base, but viewed by the userfrom feet to head. This means that the first fame number will start atthe heart apex and the last frame is toward the base and that thepatient's right side is the viewer's left and vice-versa. Input 516 isthe decay correction parameter and this allows the user to turn on oroff decay correction for processing. Decay correction is applied to boththe gSPECT data and the summed image created in quantitative processing.The computer system 120 will obtain the required decay coefficient froma decay data table and apply the correction to the created image data.The save parameters 511 allow the user to determine which files to saveto disk 104. If gSPECT files are selected then all of the files requiredto display the images within the gSPECT display procedures are saved. Ifthe individual files item is selected then files such as transverse,oblique, short axis, horizontal and vertical long axis are saved as theindividual files as displayed on the screen. The individual files aresaved as fields that can be displayed within other display applicationssuch as myocardial displays. If the parameter for both is selected thengSPECT data files and individual image files are saved as the two abovemethods increasing storage requirements.

The save objects parameters 540 illustrated in FIG. 5 indicate theobjects to be saved as those having a corresponding box checked. Thesave objects parameters affect two functions of the present invention.First, on the process screen, the user will not be required to definethe oblique images or save limit lines for the oblique volume definitionif the user has specified only the transaxial image to save. If the userspecifies only the short axis image to save then only the limits lineswill appear on the horizontal axis image. If the user specifies that allof the images will be saved, then the limits will all appear and havethe same functionality as will be discussed to follow. If the rawtransverse item is the only selected image then an error message mayappear if qualitative mode is selected since gSPECT display proceduresrequire short axis images. The second function of the save objects 540is to designate a particular extension associated with each file(extensions used are:₋₋ Tr, ₋₋ Sa, Ha, and₋₋ Va for transaxial, shortaxis, horizontal, and vertical respectively).

Referring still to FIG. 5, if the reoriented transverse (short axis)item is the only selected option then the transverse and oblique imageswill require axis definition but the vertical long axis image will notappear in the bottom frame 635. Also, the short axis image in the firstframe of the bottom row would not allow limit definitions (by verticaland horizontal volume limits lines) since the horizontal and verticallong axis dataset images created from this image are not selected forstorage. The horizontal long axis image does not require creationlimits. If the Coronal (horizontal long axis) is the only optionselected an error message may appear if qualitative mode is selectedbecause the gSPECT display procedures require short axis images. If theSagittal (vertical long axis) is the only selected option, thetransaxial and oblique images display and require axis definitions. Theshort axis image 694 and the vertical long axis image 696 display intheir appropriate viewports with the short axis image requiring creationdefinition.

The parameters 530 of FIG. 5 relating to the segments to process allowthe user to select any variation of the 8 or 16 gated segments of theR-R interval for the reconstruction process. In many cases for gatedSPECT, the user will want only to process two segments, the end-diastoleand the end-systole gated segments. Parameters 530 allow the user toselect only those segments that are necessary for their particularmethod of processing and interpretation. Note that although the user canselect a subset of the projection data, during the review the user willbe able to display any projection angle image in cine (animated) motion.It is appreciated that the present invention requires at least onesegment box to be selected to process a gated SPECT study. The userselects the proceed region 563 which transfers the user from block 420to the procedures of the computer system 120 related to the mainprocessing screen 435 when the parameters of the parameter screen areconfigured.

Processing Screen and Procedures 435. The procedures 435 of the computersystem 120 related to the processing screen of the present invention aredescribed in relation to the processing screen as shown in FIG. 6. Theprocessing screen procedures allow the user to reconstruct thetransverse and oblique images based on upon the parameters selected inthe parameters screen. When the screen initially appears a selectedimage 620 from a particular projection angle of the raw gSPECT data ispresented in window 641. The lowest numbered segment selected by theparameters 530 of FIG. 5 is displayed initially. However, by selectingthe select segment cycle field 682 alternative segments may beintroduced into the window at the same projection angle. Also found aretwo horizontal lines 610 and 611 that traverse across the window 641.These lines are used to select the region of the raw gSPECT data forreconstruction and are called the transaxial limits. The cursor 5 andmouse 107 may be used to select one horizontal limit line at a time andadjust the line vertically. As the line adjusts up and down, the pixelnumber represented by the line position is displayed next to the line.In FIG. 6, pixel 35 is selected by line 610 and pixel 55 is selected byline 611. These two limit lines and associated pixel ranges are used inpart to select the raw data limits (i.e., those frames within thehorizontal lines) to be utilized for the reconstruction procedure 450 byselecting a center volume or slice of data that falls between theadjustable limit lines 610 and 611. Once a suitable data range to theuser has been selected by the user, the reconstruct selection field 686is activated and the full volume of the image data for a particularsegment will be quickly reconstructed using the selected parameters bythe reconstruction process 450 and a single transaxial image framedisplays in 625. The image processing output from a single slice of thefull volume will be utilized to determine the azimuth and elevationparameters for oblique reconstruction. In effect, activation of 686causes only a preliminary reconstruction output of a small portion ofthe image data that will be used to determine elevation and azimuthvalues.

Once these display orientation parameters have been set, as well asother filter parameters, the final reconstruction processing of all theimage data selected within three sets of volume limit lines 658, 659 and651, 652 and 655, 657 will be performed and displayed in the displayprocessing. It is appreciated that the reconstruct selection field 686only performs the reconstruction processing for the full volume of thesegment selected of image data for each projection angle and the resultsof this preliminary transaxial reconstruction are used basically toselect the azimuth and elevation parameters. Once selected, the totalselected image data is reconstructed by activation of the process key685.

When the preliminary reconstruction completes, a transaxial displayimage 692 will appear in window 625 of this reconstructed slice. Oncethe full volume for one segment is reconstructed, the user can advancethe transaxial slices (frames) forward and backward using the arrow icon670a. This action will cause the computer system 120 to display a newtransaxial image each time the arrow icon 670a is selected Whensatisfied with the displayed transaxial image 692, the user places thecursor 5 in the transaxial viewport 625 and may adjust the alignment ofthe line 690 (i.e., the line is dragged) from apex to base of the image692 to provide proper orientation. This movement of the line 690 definesthe azimuth degree offset of the heart and will generate a vertical axisimage 693 in the viewport 630 to the right when defined. The user candefine the azimuth parameter as many times as required and the computersystem 120 will generate an oblique image 693 in viewport 630 for eachadjustment. The azimuth angle selected will be displayed in numeric formwithin the processing screen of the present invention, here 45 degrees.

Referring still to FIG. 6, when satisfied with the selected azimuthimage, the user places the cursor in the vertical axis viewport 630 andusing the cursor, modifies the alignment of line 691 so that it extends(i.e., the line is dragged) from apex to base of the heart to define theproper heart elevation for the reconstruction process. Upon definingboth azimuth and elevation angles, three images are then calculated bythe computer system 120 of the present invention and displayed in theshort axis display 641, the horizontal axis display 640, and thevertical axis display 635. The user can redefine the elevation as manytimes as required. If the user redefined the azimuth, then the elevationmust also be redefined and new short, horizontal and vertical axisimages are computed. A marker appears marking the center of the slicevolume of the transaxial image 626a, the vertical axis image forelevation determination 626b, and the short axis image 626c. Theelevation selected will be displayed in numeric form within theprocessing screen, here -26 degrees. The user can advance any of theimages by frame advance arrows 670a, 670b, 670e associated with theparticular image viewport 625, 630 and 641, respectively.

There are three pairs of limit lines that are used to select the finalreconstruction volume for storage by selecting particular pixel rangesof the raw gSPECT data for use by the reconstruction procedure 450 ofthe present invention to generate the reconstruction images. The shortaxis viewport 641 allows selection of both the horizontal and verticallong axis pixel limits. The horizontal long axis viewport 640 allowsselection of the short axis pixel limits. The cursor 5 may be positionedon any of the limit lines to adjust the pixel location. The purpose ofpair 651, 652 and pair 655 and 657 is to allow the user to define thereconstructed volume to save for the saving of both of the vertical andhorizontal long axis image sets. Lines 651 and 652 are used to set thelimits for the horizontal long axis range. The pixel number selected bya particular limit line is also displayed in numeric form, for exampleaccording to the positions of limit line pair 651 and 652 the pixelrange from 21 to 44 has been selected for the horizontal long axis slicedimension. The purpose of pair 658 and 659 is to define the short axisimage sets. According to the positions of limit line pair 655 and 657the pixel range from 52 to 18 has been selected for the vertical longaxis slice dimension. Within the horizontal viewport 640, according tothe positions of adjustable limit line pair 658 and 659 the pixel rangefrom 14 to 49 has been selected for the short axis slice dimension. Theabove pixel ranges (volume limits) will be utilized to define the finalvolume for storage by block 450.

It is appreciated that the limit lines are color coded as well as theviewport perimeters for viewports 641, 640 and 635 for ease ofidentification within the present invention. To this extent, limit lines651 and 652 as well as viewport 640 perimeter are green, limit lines 655and 657 as well as viewport 635 perimeter are blue, and limit lines 658and 659 as well as viewport 641 perimeter are red. Throughout thepresent invention, with reference to screen orientation, the color redis used to indicate data representing the short axis view and dataset,green represents data for the horizontal long axis view and dataset andblue is used to represent data of the vertical long axis view anddataset. Once the final process selection 685 is activated, the computersystem 120 begins processing of the image data based on the inputparameters using process block 450. The application will process all ofthe raw gSPECT data within the limit lines 610 and 611 and will onlyreconstruct the volume identified by limit lines 651, 652 and 655, 657and 658, 659. Each selected segment of the cardiac cycle will also beprocessed.

The user can select the change parameters selection field 681 to advanceto the parameters screen. This allows the user to change any of theinitial parameters set. The user can only select this option before theprocess selection field 685 is activated for final reconstructionprocessing. The user can also activate the selected segments selectionfield 682 which causes the computer system 120 to display a list of theavailable gated segments for selection. The list is determined based onthe checked boxes 530 of the parameter display. This selection field isonly available for selection before the process selection field 685 isselected. The user may also select the filter parameters selection field683. This selection causes the computer system 120 of the presentinvention to advance to the filter screen (discussed below) where theuser can modify the filter parameters selected and used forreconstruction. Updating these parameters will affect the parameterscreen and the filter screen. The filter parameters selection 683 isonly available before the selection of the processing selection field685. Also, the user may select the review selection field 684 which willadvance the computer system 120 to the review screen (discussed below).The review screen also allows observation of the selected segments (ofthe parameter screen) both in projection cine and gated cine mode. It isappreciated that via the processing screen, the user can select any ofthe five update arrows 670a-670e and step the image frames in thecorresponding viewports 625, 630, 696, 640, and 641, respectively, byslice increments by either increasing or decreasing order.

Total Reconstruction Processing. It is appreciated that once theazimuth, elevation, filter parameters, selected gated segments volumelimits, and transaxial limits are defined, the final reconstructionprocess by the computer system 120 may be initiated by the user based onthe three pairs of volume limit lines plus the transaxial limit lines610 and 611. This occurs by the user selecting process selection 685.The entire processing time is based on the volume of image data selectedby the volume limit lines, as well as the parameters set by the dataacquisition computer 20 and the volume of raw gSPECT data selected bylimit lines 610 and 611. However, a maximum processing time isapproximately one and one half minutes to two minutes. Only the selectedsegments will be reconstructed and saved. During the processingprocedure, the quit selection field 687 may be activated by the user toterminate the present processing task of the present invention. It isappreciated that there are a number of well known processing proceduresfor back projection reconstruction, or tomography as it may be known,based on a given set of gated SPECT input and selected reconstructionvalue. The present invention may operate equally well with a number ofsuch well known reconstruction processes and they may be advantageouslyused within the present invention as applied via the computer system120.

The reconstructed volumes are saved to disk 104 by the computer system120 and those saved are a function of which image datasets are selectedfor storage by the parameters screen. If the transaxial image is theonly image marked to save, then the option to generate the obliqueimages is not available within the computer system 120. If any of theoblique images are marked to save then all of the oblique images arecomputed. If the short axis image is marked to save then the only limitlines that appear in the processing screen are the limit lines displayedon the horizontal axis image in viewport 640. If the horizontal orvertical axis are marked to save then only limit line that appear arethe limit lines on the short axis image in viewport 641.

As a result of the total reconstruction process 450, the presentinvention will generate four datasets each representing a series ofslices of the reconstructed volume, a transaxial series dataset, a shortaxis series dataset, and vertical and horizontal long axis seriesdatasets. The number of image frames in each series depends on the pixelranges selected for that series by the limit lines selected within themain processing screen and the pixel length of each slice. The displayprocesses of the present invention provide various methods andmechanisms to display and quantify the data within the image frames ofthese three series or datasets.

Filter Screen and Procedures 430. The user will advance to the filterscreen of the present invention by selection of the filter parametersselection 683 from the processing screen. The filter screen and relatedprocessing tasks of the computer system 120 allow the user to select thetype of image reconstruction filter as well as the filter parameters foreach selected filter type in detail. The purpose of the filter screen isto allow the user to visually inspect the reconstructed images basedupon any user defined filter combination or filter set. The filterscreen is shown in FIG. 7. By displaying results of various filterparameters, the present invention allows the user an opportunity toobserve and select the filter set that provides the best image for thereconstruction data.

Refer to FIG. 7. Specifically, the proceed selection 710 may be selectedby the user via cursor 5 to accept the filter and/or parameters selectedby the user which are currently displayed in viewport 720 and also toadvance the user to the processing screen 435 of the present invention.Any changes recorded by computer system 120 will become the defaultparameters for processing and will be reflected in the text fieldlocated on the filter screen and the cycle fields located on theparameters screen. The cancel selection field 740 when activated by theuser will reject all changes to the filter parameters and returns theuser to the processing screen. The current cutoff text field 766 informsthe user of the current filter cutoff value selected. It is updated bythe computer system 120 every time the cutoff value of the filter curvegraph is changed via keyboard control and input 776. The current filterorder text field 767 is a text field informing the user of the currentorder value selected by the user via keyboard control and input 777. Itis updated according to user interaction. The type of filter selectedfor use is entered via cycle field 774 and is called the window cyclefield. When selected by the user, via the cursor, a pull down window 775may also be displayed illustrating all of the well known filter typesthat are available for the present invention (i.e., Butterworth,Guassian, Hamming, Hanning, Ramp, and Parzan). The user may use thecursor 5 and the mouse to select (i.e., highlight) a particular filtertype for use in reconstruction processing 450.

Displayed in the filter screen of the present invention in viewport 715is a raw gSPECT projection of the current gated segment of the ECTimage. The same horizontal reconstruction limit lines 610, 611 arepresent as discussed in the processing screen. These limit linesdetermine the volume of interest for the filter selection and determinea midpoint slice for analysis. These limit lines may be adjusted(dragged) by the cursor 5 to define a new midpoint (the default limitlines are those as defined by the processing screen). There are alsofour viewports 721, 722, 723 and 724 each containing the same image (butbased on an independent filter set) defined from the midpoint slice ofthe limit lines outlined on the raw data image of viewport 715. Thefilter name text field associated with each viewport indicates thefilter type and parameters for that specific image in the associatedviewport. All four viewports can have a different set of filterparameters.

Each viewport image of the above may be independently configured withseparate filter parameters. The filter parameters are adjusted for eachof the four viewports by first using the cursor 5 to select a particularviewport by activating the viewport region on the display screen 105.The selected viewport will then be highlighted by a set of four bluecorner tabs 765 which surround the selected viewport and the filterparameters for that viewpoint will be displayed in viewport 720. In FIG.7 the currently selected viewport is viewport 724 and is shown selectedby tabs 765. The filter set for this selected viewport is thereforegenerated in viewport 720 by computer system 120. Information regardingthe selected filter parameters for each viewport is also displayed nearthe associated viewport for display including the filter type associatedwith each image. For instance, viewport 721 has associated informationregarding: (1) the cutoff value; (2) the order; and (3) the filter nameof the filter used. The same is true for viewports 723, 722, and 724.

The computer system 120 will reconstruct one slice (the center slice) ofthe raw gated SPECT data for all projection angles using the currentfilter parameters for each of the four viewports and display an imagefor each. Each time the viewport is selected and the filter parametersare modified for the selected viewport, the computer system 120 willreconstruct the new image. Only the selected viewport will change inthis case. The center slice location may be modified by movement of thelimit lines 610 and 611. Once a new center line is selected, the displayfor all viewports will update to reflect the new slice reconstruction.It is appreciated that only one viewport is active at any given timeaccording to the present invention and only the active viewport changesaccording to modifications in the filter parameters.

Beneath the raw data viewport 715 is the filter function graph viewport720. This graph is the same graph utilized within the SPECTreconstruction program indicating the amplitude (y-axis) and thefrequency (x-axis). The graph will correspond to whichever of the fourviewports is currently selected by the user (i.e., highlighted with theblue corner tabs 765); adjacent to the viewport 720 for the filter is anindication 795 of which viewport image is associated with the currentlydisplayed filter information, This indicator may also be displayedbeneath the filter viewport 720. The viewport indicator 795 will changeas new viewports are selected by the user. The filter graph viewport 720contains two keyboard control inputs 776 and 777 which allow for usermodification of the cutoff value and the order, respectively. When a newvalue for any of these two are input, the appropriate filter graphs 751and 752 will update in time. Filter graph 751 represents the selectedwindow and graph 752 represents the filter function. Further, underkeyboard or cursor control, the type of filter can be selected via cyclefield 774 and/or window 775. Upon selection of a new filter type (or anew cutoff value or a new order value), the filter graph in viewport 720will update as well as the currently selected viewport image, in thiscase the image in viewport 724.

It is appreciated that when the proceed 710 selection is activated bythe user the filter parameters set corresponding to the currentlyselected viewport (i.e., the viewport highlighted by the blue tabs 765)will be selected as the filter parameters used for the finalreconstruction processing 450. In other words, the filter screen of thepresent invention gives the user another avenue to input the filterparameters of the parameter screen. It is appreciated that the filterscreen is advantageous because of the ability to illustrate multipleviewport images corresponding to different filter parameters forcomparison and selection purposes. It is also appreciated that selectionof either cancel 740 or proceed 710 will instruct the computer system120 to return to the processing screen. Selection of cancel 740 returnsto the processing screen without entry of the modified filterparameters.

Review Screen and Procedures 440. The user will advance to the reviewscreen and related procedures 440 of the present invention uponselection of the view selection field 684 of the processing screen. FIG.8 illustrates the review screen. The purpose of the review screen is toallow the user a quick and efficient method to review the raw gSPECTdata and provides multisegmental visualization of the raw gSPECT data.Within the review screen, the user can cine a gated segment of SPECTdata or cine a SPECT azimuth's gated data. The review screen is designedwith four view ports, the two on the left 810, 820 display therespective raw SPECT images while the right viewports 815, 825 displaythe respective raw gated images. Therefore, the user can view thesegments selected in either projection cine or gated cine. Typically thesegments selected will be end-diastole and end-systole, however any twosegments selected for reconstruction may be displayed.

Referring to FIG. 8, viewport 810 displays the raw gSPECT image data fora selected gated segment. Typically this segment would be theend-diastole segment. By selecting a viewport with the cursor 5, a setof blue comers 865 will highlight the selected viewport Here theselected port is 820. According to the present invention, the viewports810 and 820 display the raw gSPECT information for the selected segmentsrespectively. The user may select, via cursor 5 or keyboard 106 control,to animate (cine) the image in any of the two viewports 810 or 820through the projection angles that were collected by the imaging camerasystem 10. This is called cine of the raw SPECT data for a givensegment; as the image cines, the image data (gSPECT) for currentprojection angle is displayed on the screen 870 and 871. It isappreciated that present invention allows the rate of cine motion to beincreased or decreased according to user control. The images 850 and 851are a representation of this cine motion through the angles ofprojection that the detector 12 rotated through when collecting theimage data for the selected segments 1 and 2 respectively. Theseselected segments refer to the segments that were originally selectedfor imaging at the parameters screen. According to the display of FIG.8, the viewport 810 cines (by angle) the end-diastole phase of thecardiac cycle while viewport 820 cines (by angle) the end-systole phaseof the cardiac cycle, both in synchronization according to the givenprojection angle.

It is appreciated that when selected viewports 815 and 825 of thepresent invention display an image at a particular projection angle thatcorresponds to viewports 810 and 820 respectively for a particularselected segment. These viewports 815 and 825 are the gated viewportsand will cine according to the gated segments of the R-R interval forone particular projection angle. When these viewports 815, 825 cine, theentire cardiac cycle may be viewed by animation according to aparticular projection angle that may be determined by viewports 810 and820. The projection viewports 810 and 820 will cine the respective imagefor the 1-128 projection angle frames (depending on the number ofselected frames in data acquisition). The gated viewports 815 and 825cine the respective image for the 1-16 gated segment frames (dependingon the number selected in data acquisition).

More specifically, in order to control the cine function of the images,a cine function selection region from an image control selection fieldmust be activated by the user, this is accomplished by activating a cineicon using cursor 5. When all of the viewports are selected and cine isturned on by the user, the gated images of viewports 815 and 825 willbegin to cine immediately through the segments of the R-R interval for agiven projection angle. When the cine function (i.e., by angle ofprojection) is initiated for the viewports of the raw SPECT data at 810and 820, the gated images within viewports 815 and 825 will "freeze" andthe SPECT images in viewports 810 and 820 will begin to cine throughprojection angles for a particular segment. When the SPECT images of thepresent invention in viewports 810 and 820 are paused by action of thecursor, the gated images in viewports 815 and 825 will again begin tocine (i.e., by segments of the cardiac cycle) but will be displayedaccording to the angle of projection displayed by the correspondingfrozen frame of the SPECT images of viewports 810 and 820. It isappreciated that the present invention controls the projection angle forthe images of the viewports 815 and 825 according to the projectionangle represented within viewports 810 and 820 once paused. It isappreciated that according to the present invention, the gated images ofviewports 815, 825 cannot be controlled for pause, start, or step viathe images in the viewports 810 and 820.

Duplication of the SPECT images (i.e., viewports 810 and 820) andduplication of the gated images (i.e., viewports 815 and 825) isimplemented by the present invention in order to present end-diastole(ED) segment and end-systole (ES) segment, top and bottom respectivelyIt is appreciated that selector and cycle field 832 allows the user toselect a different segment for the top views (viewports 810 and 815)while selector and cycle field 833 allows the user to select a differentsegment for the bottom two views (viewports 820 and 825). For instance,cycle field 832 can be selected by cursor 5 and a list of the selectedsegments from the parameter screen will be presented, i.e., a differentsegment from the list will be displayed each time the cycle field isselected A selector button on the mouse 107 can then be used to selectthat particular segment displayed for the corresponding viewports (fortop or for bottom).

It is appreciated that for clarity both the projection cine (i.e.,viewports 810 and 820) and the gated cine (i.e., viewports 815 and 825)cannot cine at the same time. But the two projection images withinviewports 810 and 820 or the two gated images in viewports 815 and 825or one projection (i.e., viewport 810) and the other gated (i.e.,viewport 825) can cine at the same time according to the presentinvention. Within the review screen, the present invention provides acancel selection field 840 and when activated will return the user tothe processing screen. There are no parameter changes allowed within thereview screen.

The present invention allows a pop up window 890 which is displayed byselection of an icon by user control with cursor 5. This window allowsfine adjustment of the image display features of the present inventionas described above with reference to the selected segment evidenced bythe selection corner tabs 865. A step field 891 when activated each timewill step, frame at a time, the cine motions of the display images. Thepause 892 field will cause the images in viewports 810 and 820 to pauseand will therefore allow cine motion of the gated viewports 815 and 825according to the paused projection angle. The selections for beginning893 and end 894 define a sub-range of the projection angles that can beused for the projection cine. There is also a rate cycle field 897 thatis used to control the rate of the cine motion of the viewports. Thereis also a direction field (not shown) that controls the directionthrough which the frames are displayed for projection cine (i.e., fromend to last or from last to end).

Generally, it is appreciated that the user can advance to any of thescreens (i.e., parameter screen, processing screen, filter screen,review screen) to change any of the parameters during the processingsequence of the present invention as long as the process selection field685 has not been selected for final processing. This includes thereconstruction selection field 686 as well.

SECTION IV--Display Procedures and Related Screen Displays on Display105

Once the image data is acquired and processed, as discussed above, thereconstructed images are displayed according a variety of differentdisplay processes that are compiled within the display process 900 ofthe present invention. FIG. 9A illustrates main aspects of the displayprocesses executed by the post acquisition computer system 120 of thepresent invention. Once final reconstruction has been selected andaccomplished via block 450 (not shown in FIG. 9A), procedures of theprocess data block 400 send the reconstructed image data to a maindisplay process block 910 which contains the main display screen. Thereconstructed data is saved to disk 104 in multiple series of datasetframes, one for each of the three display orientations and further theabove is saved for each selected segment of the R-R interval. The entirefile may be saved as a single object in storage device 104. Thisinformation is made accessible to the display processes 900. From themain display screen processing 910, a three dimensional (3-D) processingblock 920 displaying 3-D screen information can be entered via useractivation of a 3-D selection field. Also, the present invention allowsthe user to enter an images display process block 930 that contains animage screen of multiple data set frames. Third, the present inventionallows the user can activate a quantify selection region to enter thequantify display screen processing 940 of the preferred embodiment ofthe present invention. From the quantify display screen processing, asubset processing block 950 can be entered which performs particulargraph display processing of the information presented in by block 940. Asubset processing 1510 of block 940 is performed to compute and displaythe quantitative functional display rings of the preferred embodiment ofthe present invention. The user exits the display processing routines900 of the present invention by activating a quit selection region 1028which is available from the main display screen and upon activation thequit and return processing 990 are entered. From any processing of the3-D screen 920, the images screen 930, the main screen 910 or thequantity screen 940, any of the other three screens may be entered. Thisaspect of the present invention is shown by the flow director 905. Flow905 couples entry of processing blocks 910, 920, 930, and 940. Block 950is entered only from block 940.

It is appreciated that the functional images of the preferred embodimentof the present invention that display both information regarding wallmotion and wall thickening are generated and displayed within theprocessing blocks 940 and 950, and more specifically within processingblock 1510 (FIG. 15) of block 940.

FIG. 9B represents the data structure utilized by the display proceedingblocks of the present invention. FIG. 9B illustrates three datasets 481for a given segment of reconstructed data The short axis dataset 481a,the vertical long axis 481b and the horizontal long axis 481c areillustrated within the structure 481. Each dataset is composed ofoblique (orthogonal) image frames of the reconstructed volume for agiven segment and FIG. 9B illustrates the viewing orientations for eachof the three datasets. The short axis image frames 964 (here four framesare shown) are viewed from the viewing direction indicated by 965 andrepresent a top view of the oblique slices of the volume as shown. Thevertical long axis frames 968 (four are shown) are viewed from 966 andrepresent a side view of the oblique slices of the volume as shown.Lastly, the horizontal long axis frames 969 (four are shown) are viewedfrom 967 and represent a frontal view of the oblique slices of thevolume as shown. During triangulation, as discussed below, vertical andhorizontal cross hairs may be positioned within a frame (say frame 2) ofthe short axis dataset to select a particular frame (say frame 1) of thevertical long axis dataset and a particular frame (say frame 3) of thehorizontal long axis dataset It is appreciated that the number of slicesselected for each dataset and the volume of the reconstructed volumerepresented by the slices are determined based on the three pairs ofvolume limit lines discussed above.

Main Display Screen Processing 910. The user automatically enters themain display screen processing 910 upon completion of the finalreconstruction processing 450 of the image data (i.e., the task enteredafter the process 685 selection region is activated). It is appreciatedthat after final reconstruction processing, only the image data withinthe selected volume represented within the limit lines (1) for the shortaxis 658, 659, (2) for the horizontal long axis 651, 652 and (3) for thevertical long axis 655, 657, will be supplied and saved for display.Depending on the slice thickness, as defined in the parameters screen,this selected volume will be used to create different series of frameimages. For instance, assuming the slice thickness was one pixel, thenumber of frames for the short axis view series should be 36 because theshort axis limit lines traverse pixels 14 to 49 as shown in theprocessing screen. The number of frames for the horizontal long axisview series is 24 because the horizontal long axis limit lines traversepixels 21 to 44. The number of frames for the vertical long axis viewseries is 35 because the vertical long axis limit lines traverse pixels18 to 52, as illustrated by the processing screen of FIG. 6.

The main display processing screen is illustrated in FIG. 10. Imageinformation is displayed for two selected segments, segment 1 andsegment 2. Typically the selected segments are end-diastole andend-systole. However, any two segments from the parameter screen may beselected for display. Segments are selected by using the segment cyclefields 1068 and 1070. One display segment is selected using the 1068cycle field by placing the cursor 5 over the cycle field and activatingthe mouse 107, each time the mouse is activated a new segment within thecycle list is selected and displayed. The other of the two displaysegments is selected using the 1070 cycle field by placing the cursor 5over the cycle field and activating the mouse 107; each time the mouseis activated a new segment of the cycle list is selected and displayed.

Refer to FIG. 10. The main display screen contains 14 viewports. Eachviewport contains 256×256 pixel resolution within the display screen105. The top row of viewports 1030, 1036, 1048, and 1054 contain thereference images of both the segments selected and typically representthe end-diastole (viewports 1030, 1036) and end-systole (viewports 1048,1054) images. These reference images are selected by the presentinvention as short axis and vertical long axis images of center or midslices of the reconstructed data. For the end-diastole segment, theupper left viewport 1030 represents the short axis image 1080 of themyocardium and the other left viewport 1036 represents the vertical longaxis image 1082. For the end-systole segment, the upper right viewport1048 represents the short axis image 1084 of the myocardium and theother left viewport 1054 represents the vertical long axis image 1086.The upper viewports are separated by box 1042 that contains the segmentselect cycle fields for segment selection.

Each of the upper row viewports contains pairs of locator bars that areuser adjustable and can be moved up or down or right or left, as thecase may be, by the cursor 5. Each bar of a pair will move together, andany bar of a pair may be activated to adjust both bars. These locatorbars are used to select the particular image frames of a dataset todisplay in the remaining 10 (lower) display viewports. It is appreciatedthat the locator bars are color coded such that bars 1091a, 1091b and1096a and 1096b are blue, bars 1090a, 1090b and 1095a, 1095b are greenand bars 1092a, 1092b and 1097a, 1097b are red. Specifically, viewport1030 contains two bar pairs 1090a, 1090b and 1091a, 1091b and thereference short axis image 1080. The first pair 1090a, 1090b of thepresent invention indicates the position (with reference to the image1080) of the frame number of the horizontal long axis view dataset todisplay in viewport 1056 with reference to the first segment (ED). Aseither bar 1090a or 1090b is moved up or down on the display, the imageframe within viewport 1056 increases or decreases in frame number from aminimum of 1 to a maximum of the frames in the horizontal axis dataset(here 24); in this example, the frame indicator 1057 illustrates thatfame 12 has been selected for display by the bars. The pair 1091a, 1091bof the present invention indicates the position (with reference to theimage 1080) of the frame number of the vertical long axis view datasetto display in viewport 1050 with reference to the first segment (ED). Aseither bar 1091a or 1091b is moved right or left on the display, theimage frame within viewport 1050 increases or decreases in frame numberfrom a minimum of 1 to a maximum of the frames of the vertical log axisdataset (here 35); in this example the frame indicator 1051 illustratesthat frame number 15 has been selected for display by the bars. Theshort axis viewports (1032, 1038, 1044 and 1034, 1040, 1046) illustratea series of views for each segment With reference to viewport 1036, ahorizontal long axis image 1082 is shown and within this viewport bars1092a, 1092b of the present invention indicate the position (withreference to the image 1082) of the frame of the short axis view datasetto display in viewport 1032 with reference to the first segment (ED). Aseither bar 1092a or 1092b is moved up or down on the display, the imageframe within viewport 1032 increases or decreases in frame number from aminimum of 1 to maximum of the frames in the short axis dataset (here36); in this example, the frame indicator 1033 illustrates that framenumber 12 has been selected for display by the bars. It is appreciatedthat viewport 1038 will then display the next short axis frame number,here frame number 13 at 1039 and the next viewport 1044 will display thenext short axis frame number, here frame number 14 at 1045 for thissegment (ED). The series of viewports displayed here for the short axispresentation comprise viewports 1032, 1038, and 1044 for the ED segment(i.e., the first selected segment).

It is appreciated that the above description applies equally to thedisplay processing of the present invention for the other segment (i.e.,the ES segment), except different viewports are involved. For instance,viewport 1048 illustrates the short axis reference image 1084 for theend-systole (ES) segment and contains locator bars 1095a, 1095b and1096a, 1096b. Locator bars 1095a, 1095b control the horizontal long axisframe image number (here frame 12) that is displayed in viewport 1058,these bars may be adjusted to alter the frame number in the viewport.Locator bars 1096a, 1096b control the vertical long axis frame imagenumber (here frame 15) that is displayed in viewport 1052, these barsmay be adjusted to alter the frame in the viewport. Viewport 1054illustrates horizontal long axis reference image frame 1086 and containslocator bars 1097a and 1097b. Locator bars 1097a, 1097b control theshort axis frame image number (here frame 12) that is displayed inviewport 1034, these bars may be adjusted to alter the frame in theviewport. Viewport 1040 displays the next short axis frame number, here13 and viewport 1046 displays the next short axis frame number, here 14.It is appreciated that the reference images (i.e., 1080 and 1082 for EDand 1084 and 1086 for ES) for each segment are a composite of the shortaxis and a composite of the horizontal long axis. Series viewports 1032,1038 and 1044 represent the ED segment short axis image frames while theviewports directly beneath them 1034, 1040 and 1046 represent thecorresponding ES segments data frames. The user may compare the dataframe images effectively using such display. The same is true for thevertical and horizontal short axis data frames for ED and ES segments(i.e., viewports 1056, 1058 and 1050, 1052, respectively).

For each segment, after the user selects the location of bars 1092a and1092b (for the end-diastole segment), the present invention instructsthe computer system 120 to compute the short axis image set and displaysthe first three frames referenced from the locator bars in viewports1032, 1038 and 1044 respectively. The same is true for the end-systolesegment with regard to viewports 1034, 1040 and 1046. After the userselects the location of bars 1090a and 1090b the present inventioncomputes the horizontal long axis series and displays the first framereferenced by the locator bars in the viewport 1056. The same is truefor the end-systole segment regarding viewport 1058. After the userselects the proper location of bars 1091a and 1091b the presentinvention computes the vertical long axis series and displays the firstframe referenced by the locator bars in the viewport 1050. The same istrue for the end-systole segment regarding viewport 1052.

Referring still to FIG. 10, the present invention provides the abilityto frame advance any of the image frames through the respective datasetwithin the bottom 10 viewports. For instance, using arrow indicators1060 and selecting viewport 1032 with the cursor 5, the user may advanceor decrement the displayed short axis ED frame through the ED short axisdataset by one each time the mouse 107 is activated. Each time the shortaxis image at viewport 1032 is updated, the viewports 1038 and 1044update accordingly in series fashion. The same is true for viewports1034, 1040 and 1046 for the short axis ES images using arrow field 1064and selecting viewport 1034. The vertical long axis ED image frame atviewport 1050 may be selected using the cursor and the arrow fields maybe activated to increase or decrement the frame count through the EDvertical long axis dataset. The same is true for the ES vertical longaxis image viewport 1052 using arrow 1064 and selecting viewport 1052.The horizontal long axis ED image frame 1057 at viewport 1056 may beselected using the cursor and the arrow fields may be activated toincrease or decrement the frame count through the ED horizontal longaxis dataset. The same is true for the ES horizontal long axis imageframe 1059 of viewport 1058 using arrow field 1064 and selectingviewport 1058.

It is appreciated that the number of frame number increments or numberof decrements that are applied to a selected frame may be varied by theframe cycle field 1015.

The user may select any number, from 1 to the maximum frames in thestudy, and the frame number will increment or decrement by this numbereach time the arrow fields 1060 or 1064 are activated. It is furtherappreciated that a set of double arrow fields 1062 can be used accordingto the present invention to alter the frame numbers of selected ED andES images in unison and may be adjusted by the frame update number offield 1015. The above display functionality of the present inventiongives the user great flexibility to select particular structures andslices of the image datasets reconstructed image volume for the twosegments and to compare, independently, several reconstruction views,such as short axis, vertical long axis and horizontal long axis forend-diastole and end-systole.

The present invention also offers the ability to cine any of thehorizontal and vertical long axis viewport images within viewports 1050,1052, 1056, 1058 by selecting the particular viewport and selecting acine selection region with the cursor 5. The selected ED or ES viewportwill then display each of the gated segments of the cardiac cycle tocreate an animated image using the particular viewport orientation. Thethree series short axis ES images and three series short axis ED imagesmay also be displayed in cine motion, however only viewports 1032 and1034 of the series support cine motion capability. Either viewport 1032or 1034 may be selected by the cursor 5 and the cine motion selectionregion is activated. More than one viewport may be selected for cinemotion at the same time. For instance, using the above functionality,viewport 1050 and 1056 can be selected and put into cine motion so thata physician could observe both the vertical and horizontal short axisslices of the myocardium during the total cardiac cycle. It isappreciated that any of the 14 display viewports of FIG. 10 may beenlarged by a percentage less than 100% to display an expanded image ofthe displayed frame of the dataset within the selected viewport.

The frames displayed by the computer system 120 in the main displayscreen of the present invention may be independently selected accordingto the locator bars in the procedure discussed above. Given thisfreedom, there is no particular rule or reason that an object ofinterest will be displayed in each display frame of the given threeviews for ED and ES at the same time. Also, since the user is given thefreedom to define the reconstructed structure that will correspond toparticular frame number ranges within the datasets of the threeorientations, there is absolutely no guarantee that frames of the samenumber for the short axis dataset, or the vertical log axis dataset andthe horizontal log axis dataset will contain the same structure.Therefore a frame alignment process is required. The present inventionallows a selected structure in one of the three dataset views to bedisplayed in frames of all three views by adjusting the frame number inthe other view dataset until the structure is aligned in all three viewsfor ED and for ES. This frame alignment process of the present inventionutilizes triangulation processing. In order to align the particularframes of the three datasets to a selected structure, the presentinvention enables the user to activate the mouse 107 on a givenstructure of a given viewport, say viewport 1034 of the ES short axisdataset to display two crosshairs, a horizontal 1072 and a vertical 1073cross line. The user may adjust the position of either line by movementof the mouse. In viewport 1034, the position of the line 1072 willdictate the frame number to display within viewport 1058 of the EShorizontal long axis data. The position of line 1073 dictates the framenumber of viewport 1052 to display for the ES vertical long axis dataset(Refer to FIG. 9B). Adjustment of the cross lines causes the computersystem 120 to immediately compute the frame numbers of the other twoview datasets (horizontal and vertical long axis) based on the linepositions. When displayed, frame 1052 represents the vertical obliqueslice of line 1073 and frame 1058 represents the horizontal oblique viewof line 1072. Also, adjustment of crosshairs within viewport 1052 willsimilarly update frame numbers within viewports 1034 and 1058.Adjustment of crosshairs in viewport 1058 will update the frame numberof viewports 1034 and 1052. The same is true for the ED viewports 1032,1050, and 1056. The user could next select viewports 1034, 1052 and 1058for cine motion and then observe the motion of the selected objectthroughout the cardiac cycle over all three orientations (short axis,vertical and horizontal long axis).

It is appreciated that from the processing 910 of the present inventionthat displays the main display screen, the present invention allows theuser to enter an image screen processing 930 by activation of selection1020, a 3-D screen processing block 920 by activation of selection 1025and a quantify screen processing block 940 by activation of selection1027. The display screen tasks are exited via activation of selection1028, which enters the processing block 990 of FIG. 9A.

Three Dimensional Screen Processing 920. The present invention allowsthe user to enter the tee dimensional screen processing 920 from avariety of entry points, such as from the main display screen, thequantify screen and the image screen processing blocks. FIG. 11illustrates the features of the 3D screen processing block 920 of thepresent invention as displayed on the 3D screen of the computer display105. The 3D screen allows the user to create independently 3D images fortwo different segments of the gSPECT study (ED, ES). The user can selectany of the segments that have been reconstructed with use of the segmentcycle fields in viewport 1151. There are two cycle fields 1194 and 1196for selection for the two segments for display. Field 1194 selects thefirst segment and field 1196 selects the second segment.

With reference to FIG. 11, the 3D screen is displayed with eight objectviewports with the middle two largest viewports 1162, 1164 displayingempty on initial presentation; the 3D viewports 1162, 1164 are 512×512in pixel display size. These will contain the 3D reconstructed imagesfor the two selected segments. The top four viewports are separated intotwo groups by a field entry display viewport 1151. The two viewports tothe left 1150, 1152 contain a short axis and a horizontal long axisreference image respectively for the first segment. These representreference images of the segment (ED) that the user may change via acycle field 1194 within display 1151. The two viewports to the right1156, 1158 of the cycle fields represent reference images of the secondsegment (ES) that can also be changed via the cycle field 1196 within1151.

Referring to FIG. 11, the four above viewports (1150, 1152, 1156, 1158)of the present invention contain images with interactive cursor arrowsthat allow the user to change the viewing angle of the associated 3Dcalculated image. These are the reference images and are the samereference images displayed in the main display screen for the selectedsegments. The present invention provides an interactive arrow bar 1165fixed in the center that can be adjusted through 360 degrees (or ±180degrees) to represent variable azimuth values from the center of image1164 within short axis viewport 1150. The present invention utilizesthis method to input the current azimuth for display of 3D computedimage 1172 of associated viewport 1162 for the ED image. The presentinvention allows modification of the elevation of image 1172 byadjustment of an interactive arrow 1167 having a fixed center and may beadjusted through 360 degrees (or ±180 degrees) within horizontal longaxis viewport 1152. The reference images within 1150 and 1152 arecomposite images of the short axis and of the horizontal long axis imagesets for the ED segment.

Other parameters effecting the display of the image 1172 may be enteredvia window 1180 (the ES 3-D image 1174 has a corresponding window 1182),including the method 1030 of 3D computation, either surface rendering orvolumetric rendering may be selected Either process is well known. Also,a threshold value 1031 may be determined indicate the pixel intensity(count number) threshold for display. The indicated azimuth 1032 forimage 1172 is 4.2 degrees and the elevation 1033 is zero. These valuesmay be manually entered here via keyboard 106. Other selection regionsallow the view parameters to be saved and selected. The view selectionfield 1036 allows the user to view the 3D image 1172 prior toreconstruction in order to evaluate the selected parameters. The createselection region 1037 causes the computer system 120 to create the 3Dimage utilizing the desired parameters. The images may be saved by asave option. Other previously saved images may be recalled using theselect field. The depth 1034 value may be altered which defines theperspective from the user's eye to the screen of display 1162. The viewselector 1035 allows the user to select the number of views to displaythe 3D image when the image 1172 is placed in cine motion. Options arefrom 1 to 64. In effect, the present invention allows processing torotate the displayed 3D image such that all surfaces may be displayed.

Each selected segment also is provided a series image which is visiblein short axis viewport 1154 for ED and viewport 1160 for ES of FIG. 11.There are two series viewports 1154 and 1160, one for each selectedsegment. This series image is a short axis composite and is setautomatically at the entry of the 3D screen processing 920. This imagemay be gated in SPECT or gated cine depending on the selections fromcycle entries 1194. the cycle entry is set to GATED then the user mayselect a particular slice to display, here the slice is 15. According tothis selection, viewport 1154 will cine motion all of the segments ofthe cardiac cycle visible from projection angle 15 and the image 1190will beat. The cycle entry 1194 may be togged to SPECT wherein a secondselection is available for selecting a particular segment for display.When a segment value is entered, the image in 1154 will cine in SPECTmode for that particular segment for all projection angles. In effect,the viewport 1154 will display in cine motion all of the projectionangles of the SPECT study for the given segment selected. The presentinvention allows the user to frame advance and cine the series image setthrough all slices or all gated frames via viewport 1154 for one segmentor viewport 1160 for the other segment. Cycle field 1196 controls thecine parameters for viewport 1160, cycle field 1194 controls viewport1154.

The user is able to set parameters for a particular 3D reconstructionfor a given segment and independently reconstruct the two selectedsegments. To this extent, the view selection 1036 causes the computersystem 120 to generate a single image reconstructed with selectedparameters and viewing perspective. The user may control all aspects ofimage manipulation and reconstruction for a given 3D image for a givensegment without affecting the other 3D image. The create selection 1037creates a full 3D reconstruction image in viewport 1162 based on theuser defined parameters. The 3D reconstruction will be reconstructed sothat the viewing angle will cine and at the same time cine in gatedfashion. Each 3D image may cine in SPECT or cine gated (i.e., beat)according to the present invention. It is appreciated that the seriesimages of viewports 1154 and 1160 may cine in SPECT or cine gated insynchronization with their respective 3D image of 1162 and 1164. It isappreciated that the series images within viewports 1154 and 1160 may beexpanded for more database observation.

It is appreciated that viewports 1050, 1052, 1054 and 1162 (the EDsegments) may be defined and observed independently from the other setof viewports 1056, 1058, 1060 and 1164 (the ES segments). To thisextent, all of the discussions above regarding the configuration anddisplays available for the ED segments are equally available for the ESsegments. Specifically, viewport 1156 and viewport 1158 allow azimuthand elevation definition for the 3D image 1174 of viewport 1164. Theparameter window 1182 controls the display of the 3D image 1174.Further, the cycle fields 1196 control the cine motion of viewport 1160for either SPECT cine or gated cine.

From the 3D processing block 920, the present invention allows the userto activate a main selector 1120 to return to the processing routines910 or activate a quantify selector 1027 to enter the quantifyprocessing routines 940 or activate an image selector 1020 to enter theimages screen processing 930. The cancel selection 1110 cancels thecurrent function and returns to the previous display screen processingthat was entered via cycle flow 905.

Image Display Processing 930. The processing required for the imagedisplay screen of the present invention is discussed below. Theprocessing block 930 of the image display screen is designed to displayseries of frames of the short axis, vertical long axis and horizontallong axis datasets from the two user selected segments. The imagedisplay screen is illustrated in FIG. 12. This screen is designed todisplay a number of different series of image frames to the user foreach of the three datasets: short axis, vertical and horizontal longaxis, and for two selected segments (typically these are end-diastoleand end-systole segments of the cardiac cycle). The image screen of FIG.12 consists of 48 viewports in total. The viewports are configured in 8horizontal and 6 vertical frames. Each of the viewport series thatcorrespond to a particular image dataset are color coded in perimeter.The short axis viewports (1220a-1220h and 1222a-1222h) have redboundaries, the vertical long axis viewports (1224a-h and 1226a-h) haveblue boundaries and the horizontal long axis viewports (1228a-h and1230a-h) have green boundaries. The viewports contain frames of theprocessed SPECT image datasets representing the first segment shortaxis, the second segment short axis, the first segment vertical longaxis, and the second segment vertical long axis, the first segmenthorizontal long axis, the second segment horizontal long axis datasets.

The two user selected segments are selected via cycle fields 1260 and1262 for the first and second displayed segments, respectively.According to the images display of the present invention, the first rowimages (series 1220a through 1220h) are the short axis images from thefirst selected segment (ED), the second row images (series 1222a through1222h) are the short axis images from the second selected segment (ES),the third row images (series 1224a through 1224h) are the vertical axisimages from the first selected segment (ED), the fourth row images(series 1226a through 1226h) are the vertical axis images from thesecond selected segment (ES), and the fifth and six row images (series1228a-1228h and 1230a-1230h, respectively) are the horizontal long axisimages of the first (ED) and second (ES) selected segments,respectively. Each of the above series of frames display the associatedframe number of images in sequence. For instance, series 1220a-1220bdisplays the frames 12 through 19 of the short axis dataset for theend-diastole time segment.

The present invention allows the user to advance or decrement any of theabove frame series presentations by six arrow fields. Arrow field 1240will advance or decrement the frame count at viewports 1220a through1220h by using the mouse 107 and the cursor 5 to activate a particulararrow. For instance, when the advance arrow (could be right or leftselection) is selected the frame numbers of series 1220a to 1220b changefrom frame range 12 to 19 to range 13 to 20, likewise when userdecremented the series changes to frame range 11 to 18. The same is truefor the other five arrow selections. Arrow field 1242 controls the framerange for series 1222a-1222h, field 1244 controls series 1224a-1224,field 1246 controls series 1226a-1226h, field 1248 controls series1228a-1228h, and field 1250 controls the frame range for series1230a-1230h.

The frames selection 1210 allows the user to increment or decrement theseries frames, as discussed above, by any number of frames input intothis field up to the maximum frame number for the dataset. Therefore, ifthe frame cycle field 1210 is programmed as two, then the arrow fieldsabove will increment or decrement their respective frame series by twoframe numbers per selection, etc. It is appreciated that use of specialdouble arrow fields 1280, 1281, 1282 may be used to advance the framesof two frame series in unison that are representative of datasets forboth segments of the same orientation. For instance, arrow selection1281 advances or decrements the frames of series 1224a-1224h and series1226a-1226h in unison since these correspond to both ED and ES segmentsof the vertical long axis dataset orientation. By selection of a specialmouse button on 1240 a pop-up menu may be displayed (not shown in FIG.12) illustrating each frame within the short axis ED dataset and theuser may scroll down the list and pick a particular frame to display atviewport 1220a. The same is true for the other datasets of FIG. 12.

It is appreciated that the images in the first vertical column ofviewports (i.e., 1220a, 1222a, 1224a, 1226a, 1228a, and 1230a) perform agated cine controlled via a cine selector. When selected, the imageswill cine in gated fashion to display the entire cardiac function. Theimages can also be zoomed within the present invention if the frames areselected with comer tabs. However, the cine images will not maintaintheir zoom or brightness if the images are manipulated in any fashion.The present invention allows any of the images within the displayedviewport to be enlarged by selection of the viewport and activation ofan enlargement region via the cursor 5 and mouse 107. Also the images inthe first vertical column viewports support triangulation. Any of thethree ED viewports may be selected with crosshairs to selects frame ofthe other two ED viewports using the triangulation techniques asdiscussed above. The same is true for the three ES viewports of thefirst vertical column.

It is appreciated that the user may frame align the frames of variousdifferent datasets of FIG. 12 using triangulation within the presentinvention. This frame alignment is accomplished analogously to thetriangulation process described with respect to the main display screenprocessing 910. The images display screen provides the user with amethod and display format for observing a vast amount of data frames ofthe three dataset orientations of the reconstructed volume. Using such adisplay several structures of the heart can simultaneously be displayedat all three orientations at eight slice positions per orientation andfor two segments. Each orientation may also be cine gated. These datadisplay formats offer powerful tools for CAD diagnosis and imagecomparison.

Within the processing of the present invention related to the imagedisplay screen, the user may activate the main selection field 1120 toreturn to the main screen processing 910, or activate the quantifyselection 1027 to enter the quantify screen processing 940, or selectthe 3D selection field 1025 to enter the 3D processing 920. The user mayalso select the cancel field 1205 to exit the images screen processing930 and return the previously entered display screen processing block

Quantify Screen Processing 940. The quantify screen processing 940 ofthe present invention may be entered from the main display screen, theimage display screen and the 3D display screen. FIG. 13 illustrates arepresentation of the quantify display screen generated by the computersystem 120 on display screen 105 as a result of the quantify processing940. The purpose of the quantify (or quantification) screen is toprovide the user with a quantitative method and display used forevaluating myocardial perfusion (wall thickening) and function (wallmotion). Functional display rings are illustrated on the bottom row ofFIG. 13 and these functional displays correspond to associated pairs ofend-diastole and end-systole images which are displayed above thefunctional display rings. The functional displays are ring shaped andthe ring is divided into eight particular sections which are arcsections, however the number of particular arc sections may be increasedor decreased within the scope of the present invention. Each arc sectionis given a different color and is displayed with a different radialwidth depending on calculated perfusion ratios and displacement factorsassociated with sections of the related end-diastole and end-systoleregions of interest.

The following definitions are given with respect to items of thequantify screen. The circular displays (one is shown as 1351a) that aresegmented into individual pie shaped sections are called regions ofinterest or ROI. A particular pie shaped section is called a section ofthe ROI. Each viewport of the top row are frames of the end-diastolesegment of the cardiac cycle (ED), and viewports of the bottom row areframes of the end-systole (ES) segment of the cardiac cycle. Each of thetop row ED viewports, such as 1310, has a corresponding bottom rowviewport, such as ES 1312, directly beneath. The top and bottomviewports are corresponding pairs (ES/ED) because they display the samemyocardial structure (i.e., same slice frame and same short axis view)only at different segments of the cardiac cycle. Therefore, thecorresponding ROIs for these related viewport images, such as 1351a and1352a, are an ROI pair. Sections within ROI pairs are also paired, suchas section 1 of 1351a and section 1 of 1352a are section pairs becausethey identify the same myocardial section only at different segments ofthe cardiac cycle. It is appreciated, given the above, a particularfunctional ring presents information regarding the change of a givenmyocardium structure at a given slice of the reconstructed volumebetween the ED and ES segments.

It is noted that computations of the present invention to determine wallperfusion and wall motion (as discussed below) are performed onindividual section pairs for each viewport pair. Each viewport pair (ROIpair) will render a separate functional display. Each section pair willprovide information for a separate arc section of a particularfunctional display ring. Eight section pairs comprise all sections of aviewport pair and therefore provide all the information necessary tocompute all eight arc sections of a functional display ring. It isappreciated that the ROIs, and therefore the functional displays, may beindividually partitioned into any number of individual sections and that8, or alternatively 16, sections are selected options based only ondesign choice. Any number of sections is therefore within the scope ofthe present invention.

A study of the functional displays quickly provides quantitativeinformation regarding the amount of perfusion and wall motion for agiven selected myocardial structure between the ES and ED segments. Itis appreciated that ischemic areas of the myocardium will appear asareas with fair wall motion, but with little perfusion (i.e., low ratiovalue). This is the case because, according to the data as presented bythe present invention, the wall motion image data taken during theimaging session represents a rest condition. However, the perfusion datarepresents a stress condition because the radionuclide is introduced anddistributed while the heart is exercised and, as is well known, does notredistribute during the rest condition. Therefore, the present inventionallows an efficient method of comparing rest versus stress conditiondata in a single functional display without the need of performing twoimaging sessions, i.e., one at rest and one at stress based on thefunctional displays.

FIG. 13 illustrates display of a series of five images of sequentialframes (1310, 1314, 1318, 1322 and 1326) from the short axis dataset forthe end-diastole dataset. In the displayed instance, frame numbers 7 to11 are displayed. It is appreciated that all of the short axis imagesdisplayed contain brightness data representative of the concentration ofradionuclide within the displayed myocardium. To this extent theend-systole images (such as 1312) are somewhat brighter over theend-diastole (such as 1310) images for a normal heart. Also displayedaccording to the present invention beneath the above images are a seriesof five images (1312, 1316, 1320, 1324, and 1328) of sequential framesof the short axis dataset for the end-systole segment. In the displayedinstance, fame numbers 7 to 11 are displayed. It is appreciated thatimages 1310 and 1312 illustrate the same myocardial structure, howeverimage 1310 illustrates the end-diastole phase while image 1312illustrates the end-systole phase. The same is true for the other ES/EDpairs of images (such as pair 1314, 1316 and 1318,1320, etc.). Thesuccessive images represent different short axis slices of themyocardium at end-diastole and end-systole.

It is appreciated that the following discussion centers around utilizingthe ED and ES segments for analysis. However, any two reconstructedsegments may be selected by a user according to the present invention.Segment selection cycle region 1340 can be used to select the segmentfor the upper image series display screens. Segment selection cycleregion 1342 can be used to select the segment for the lower image seriesdisplay screens.

Associated with each ES/ED image pair of the present invention is aseparate functional display 1360, 1362, 1363, 1364, and 1365 which aredisplayed directly beneath the associated pairs. It is appreciated thatfunctional display ring 1360 represents an analysis of the image datafrom the ES/ED pair 1310 and 1312. In order to generate a functionaldisplay, the user must first define a separate region of interest foreach image of an ES/ED image pair. With reference to the viewport 1310,the user will position the cursor 5 into the center of the ventricle andactive mouse 107 (i.e., the mouse 107 contains activation keys) todeposit and set the center of region of interest 1351a which will bedisplayed as a small dot at this stage. The computer system 120 thenallows the user to move the cursor 5 to the outer edge of theventricular wall and activate the mouse again to establish the maximumradius of the center of interest 1351a which will be displayed as asectioned and colored circle 1351a.

The region of interest 1351a will be divided into eight equally sizedpie shaped sections which are displayed in outline form and numbered 1to 8 as shown in FIG. 13 (it is appreciated that the user can adjust theexact number of sections that divide the region of interest byactivation of the region 1355 cycle field). The section numbers start at1 and advance clockwise as shown. The user must define the region ofinterest in the first (leftmost) viewport for each of the two rows(i.e., for the ED and for the ES row). After the user has selected thecenter point and maximum radius for a region of interest, the computersystem 120 computes and displays the ROI around the displayed ventricleof the image in viewport 1310 using the center and maximum radiusinformation. The computer system 120 of the present invention thendivides the circle into eight pie shaped sections of equal area. It isappreciated that activation of the mouse 107 by the user can redefinethe center point and maximum radius of the region of interest (ROI) ifthe current ROI is not satisfactory. This action will clear the currentROI and allow the user to begin again to establish a new ROI. Thepresent invention is also provides a mode wherein the region of interestis initially displayed and sized within a given viewport (such asviewport 1310 or 1312) and the user is allowed to displace or resize theROI as needed. In this mode, upon display of the short axis image frameinto viewport 1310, a predefined ROI is displayed and positioned in thevertical and horizontal center of viewport 1310 with a diameter of 2/3of the length of the viewport 1310. The user may then change theposition or diameter of the ROI.

The ROI requires resizing depending on the size of the short axis imagesdisplayed in viewports 1310 and 1312. The size of each ROI should besuch that it outlines the edge of the myocardium displayed. Once the ROI1351a is entered and satisfactory for the end-diastole image in theviewport 1310, the user will position the cursor 5 to the center of theventricle in the end-systole image of viewport 1312. The presentinvention allows the user to define or redefine the ROI 1352a forviewport 1312 in the same fashion as described above. After the userdefines the maximum radius for the second region of interest 1352a, thefunctional display ring 1360 can be generated and displayed. It isappreciated that the ROIs for the ED and for the ES segments will notnecessarily be of the same size. The ES region of interest 1352a shouldbe of a smaller area as compared to the ED region of interest 1351abecause the ES segment represents myocardial contraction.

Once the ROIs for the ES/ED images are selected and defined by the user,the computer system 120 computes and displays an ROI for each of theother ED images as shown 1351b to 1351e for the other four ED viewports.The computer system 120 then computes and displays the ROIs for the ESimages 1352a to 1352e. It is appreciated that the user may evoke theredefine functions at any time to alter the defined regions of interestfor the display images. Upon definition of the ROIs within the quantifyprocessing the computer system 120 performs the following computationsto render the functional displays 1360, 1362, 1363, 1364, and 1365 ofthe preferred embodiment of the present invention.

Each functional display represents perfusion and wall motionquantitative information for a particular short axis ES/ED image pair.Each section of the ROIs for the ES/ED pair have a single correspondingarc section that is combined with other arc sections to form the ringdisplay. For a given arc section comparing ED to ES images, myocardialwall thickening information is represented by an arc color or shadewhile information regarding myocardial wall movement is represented bythe arc section thickness or width. Since there are eight pairedsections of each ROI pair, there will be eight corresponding arcsections of a particular functional display and the arcs are aligned ina circular fashion to create a ring structure. The ring structure isspatially analogous to the ROI ring format.

For example, arc section 1 of functional display 1360 representsquantitative data for the first sections of ROI 1351a and ROI 1352a. Arcsection 2 of the functional display 1360 represents quantitative datafor the second sections of ROI 1351a and ROI 1352a, arc 3 for the thirdsections, arc 4 for the fourth sections and so on until arc 8 of thedisplay 1360 represents the eighth sections of the ROIs 1351a and ROI1352a. It is appreciated that the other four functional displays,1362-1365, are similarly created using section information from theindividual ED regions of interest 1351b-1351e and section informationfrom the individual ES regions of the interest 1352b-1352e. The colordisplay of the functional display region 1360, as adopted by the presentinvention, is as follows, section1 is red, section2 yellow, section3blue section4 red, section5 yellow, section6, section7 yellow andsection8 red. The below discussions describe in more specificity themanner in which the present invention renders the functional displayrings.

Although the present invention allows selection of between 8 and 16sections per region of interest, the present invention adopts 8 sectionsas a default and recommended number. This is because 8 sections perregion of interest is a division that yields the best statisticalaverage for the computation of the perfusion ratio and wall movementvalues are that based on section pairs.

Computation of Myocardium Perfusion Ratio. For each ES/ED image or framepair, the computer system 120 fetches the ROIs for each short axis imageand the image data for the ED and the ES image. For each of the eightsections within each ROI the computer system will compare pairedsections of each ROI to determine the wall thickening ratio or"perfusion ratio" for that selected section pair. For instance, thecomputer system 120 will analyze all of the pixels within section1 ofthe ROI 1351a and will select only those pixels having a maximum count,i.e., a count value above 90% of the maximum intensity count for thepixels of Section 1 of ROI 1351a; these are the maximum intensity pixelsof Section 1 ROI 1351a. The computer system 120 then determines theaverage of the intensities of the maximum intensity pixels; this valueis called the averaged maximum pixels, and is referred to as "Ved" forthe end-diastole image. The computer processor then will analyze all ofthe pixels within section 1 of the ROI 1352a and will select only thosepixels having a count above 90% of the maximum intensity count of thepixels for Section 1 of ROI 1352a; these are called the maximumintensity pixels for Section 1 of ROI 1352a. The computer processor thenwill determine the average of the intensities of the maximum intensitypixels for the ES segment; this value is called the averaged maximumpixels, and is referred to as "Ves" for the end-systole image.

Therefore, the averaged maximum values are each determined by averagingall of the pixels that are above the threshold (T) of 90% of the entireintensity range of each section1 for each ROI. Specifically, Ves and Vedare determined by averaging all of the pixel intensities that exceed avalue T for each respective section. The value T is computed by thepresent invention according to the below function:

    T=Min+0.9 (Max-Min).

Where Min is the minimum intensity value of the pixels within the givensection of an ROI and maximum is the maximum intensity value of thepixels within the given section of an ROI.

Once the above value is computed, the computer system 120 determines theperfusion ratio for the first section pair of the ROIs (1351a, 1352a)according to the below function:

    Ratio (section1)=Ves/Ved.

The computed ratio should be larger than one for a normal heart becausethe contraction phase of the cardiac cycle (ES) concentrates theradionuclide and thus creates more numbers of intense pixels per unitarea over the end-diastole phase. Once the perfusion ratio is determinedfor the particular section pair, the computer system 120 will use thisratio (typically in the range of 0.9 to 1.6) as an index into a colortable that contains a different color for each 0.1 increment of ratiovalue. For instance, the color table utilized by the preferredembodiment of the present invention is illustrated in FIG. 13 as strip1372. Table I below illustrates the color look-up table adopted by thepreferred embodiment of the present invention.

This color scheme is adopted by the present invention because thesecolors provide excellent color contrast definition within the functionaldisplay rings for adjacent arc sections. A user visualizing a displayring will have no trouble associating a color of Table I with theappropriate index ratio range. This color selection is advantageousbecause it virtually eliminates the uncertainty of interpreting subtlechanges of gray scale or other color scales currently in use. However,it is appreciated that selection of specific colors is merely a designchoice and that other color schemes and color tables having highcontrast definition. Also, some variable shades of the same color (orblack and white shading) that provide suitable contrast adjacencies arewithin the scope an spirit of the present invention. In the case ofcolor shading, the present invention employs a color shading look-uptable that may be indexed by the perfusion ratio and that provides ashading value for a given color or for degrees of black and whiteshading.

                  TABLE I                                                         ______________________________________                                        Ratio Range           Color                                                   ______________________________________                                        <0.9                  Black                                                   0.9-1.0               Purple                                                  1.0-1.1               Green                                                   1.1-1.2               Red                                                     1.2-1.3               Orange                                                  1.3-1.4               Blue                                                    1.4-1.5               Yellow                                                  >1.5                  White                                                   ______________________________________                                    

Once the particular color is selected based on the color index as shownabove and the determined ratio, the present invention instructs thecomputer system 120 to shade in the arc corresponding to the firstsection of the functional display 1360 (in FIG. 13 this is labeled as"1"). The width of the particular arc measured inward toward the circlecenter (or outward, if negative) from the normal circumference of thefunctional display 1360, is determined based on the wall motioncomputations as described below. The color table 1372 illustrated on thequantity display screen illustrates to the user the selected colorformat of use. Selection 1356 allows these colors and ratio ranges to beuser defined. In some modes of operation the selections for 1355 and1356 are not user adjustable.

It is appreciated that the above computations are performed for each ofthe 8 sections of the regions of interests 1351a and 1352a and therefore8 separate arc section colors and widths are determined by the computersystem 120 for each ES/ED image pair within the functional display 1360.The above process is also repeated for the remainder of the four ES/EDpairs in the analogous fashion using the ROIs of each ES/ED pair so thatall five functional displays will have computed cardiac perfusion dataOnce the wall motion data is determined by the present invention foreach arc section, the functional displays may be rendered forobservation.

Computation of Myocardium Wall Motion. The functional displays of thepresent invention impart information regarding wall motion of themyocardium between the end-diastole and the end-systole by varying thearc thickness of each section arc of the functional display ring. Thepresent invention computes wall movement by determining a displacementfactor (D) that is based on the displacement of the location of thecenter of mass (Mx, My) of the ED image and the center of mass locationfor the ES image for a given section pair of the ROIs. The computersystem 120 performs the below computations to determine the x and yscreen locations of the center of mass for a given section pair for bothED and ES image frames: ##EQU1##

Where Px and Pv are the x location and pixel count value, respectively,of pixel P. ##EQU2##

Where Py and Pv are the y location and pixel count value, respectively,of pixel P. According to the above equations, for a given ROI section,the total intensity (count) values for each pixel within the section aresummed to yield the Total Pixel Values. The computer system 120 of thepresent invention then determines the sum of the function (Px*Pv) forall pixels within the given section and the sum of the function (Py*Pv)for all pixels within the given section and determines the Mx and Myvalues according to the above division equations. The entire process isdone for the ED frame section and also for the ES frame section todetermine two pairs of values: Mx.sub.(ed), MY.sub.(ed) and Mx.sub.(es),MY(es). The coordinates for the center of mass for the ED selectedsection is Mx.sub.(ed), My.sub.(ed) while the coordinates for the centerof mass for the ES selected section is Mx(_(es)), MY.sub.(es).

The radial distance R of each of the center of mass (Mx, My)computations to the center of the circle (Cx, Cy) of the associated ROIring is calculated from:

    R=square root (X*X+Y*Y)

Where

X=(Mx-Cx) and

Y=(My-Cy).

It is appreciated that the above computations are performed for bothcenter of mass locations, one for ED and one for ES. Therefore, thereare two circle center points as defined by coordinates (Cx, CY), one forthe ED ROI and one for the ES ROI. It is appreciated that the computerprocessor generates two radial values from the above processing, R_(ed)and R_(es) where R_(ed) represents the radial distance from the centerof ROI 1351a to the center of mass of section 1 of 1351a and R_(es)represents the radial distance from the center of ROI 1352a to thecenter of mass of section 1 of 1352a. It is appreciated that the radialdistances R of all the sections of a given region of interest arefurther processed by the computer system 120 in that the computer system120 replaces the lowest radial distance of the sections of a particularROI by the average of the two radial values of the neighboring sections.This is an enhancement processing feature of the present invention.

The computer system 120 of the present invention then computes thedisplacement factor, D, for the first arc section of functional displayring 1360 according to the below equation:

    D=R.sub.ed -R.sub.es.

The above displacement factor, D, will dictate the amount of thickness aparticular ring arc will have from the circle circumference of thefunctional display ring. For instance, if the value of D is positive,the given arc will have a thickness of D toward the center point of thefunctional display ring. If the value of D is negative, then the givenarc will have a thickness D extending away from the center point of thefunctional display ring. In either case, the color the arc area will bedictated by the particular perfusion ratio computed above for theassociated section pair. It is appreciated that the computer system 120performs the above wall motion computations for each correspondingsection pair of the ES ROI 1352a and the ED ROI 1351a to generate allthe arc widths for a particular functional display ring 1360. It isappreciated that the present invention displays a legend 1370 indicatingthe scale of the displayed wall motion displacement factor. The range isfrom 0 to 6 in the scale of FIG. 13.

FIG. 14 illustrates in more detail a sample functional display ring1405. It is appreciated that the dashed radial lines are not displayedas a part of the functional display ring, however, they are useful inidentifying arc sections that are representative of specific sectionpairs of the regions of interest for the ED and ES images. Thefunctional display ring consists of eight arc sections 1410, 1416, 1418,1420, 1430, 1432, 1435 and 1440. Arc section 1410 is the first arcsection and the other seven are numbered in clockwise fashion around thering 1405. According to the present invention, the width value,indicated as distance 1412, for the section 1410 (which corresponds tothe first section) is a positive value and indicates the amount of widthof the arc inward toward the ring center 1465. It is appreciated thatthe color of the arc 1410 will depend on the perfusion ratio computedfor the first section from the ROI data of each ED and ES image. In thisexample the color is red.

A positive wall motion value will thus have the thickness of the arcextended toward the center of the ring. A positive wall motion valueindicates that at the end-systole phase the myocardium wall moved inward(i.e., contracted toward the center of the ventricle); this would be anormal response. A negative wall motion value will have the thickness ofan arc extended away from the center 1465 of the ring. This indicatesthat the myocardium wall moved away from the ventricle center duringend-systole. This would indicate an abnormality in most cases. FIG. 14illustrates a negative wall movement value in arc 1420. Arc 1420 is thefourth section of the ring display 1405 and corresponds to the fourthsections of the ES/ED regions of interest. The movement value indicatedby 1421 is a negative number and thus the arc 1420 extends away from thering center 1465. It is appreciated that the color of arc 1420 isdependent on the wall perfusion ratio computed by the relevant sectionsof the ES/ED region of interest. In this example arc section 1420 isgreen.

For purposes of illustration the following colors correspond to theeight arc sections of functional display ring 1405. Arc section 1410 isred, section 1416 is purple as well as arc section 1418, arc section1420 is green, section 1430 is orange, section 1432 is blue, section1435 is red and section 1440 is yellow. Integration of the wall motionarc thickness and wall perfusion color coding scheme produces thefunctional display ring 1405 for a given ES/ED image pair. It is furtherappreciated that a separate functional ring is rendered for each of thefive ES/ED image pairs. Each of the eight arcs of the ring 1405 may becomposed of a separate color and may be of a separate width, somenegative and some positive. Each pie shaped section represents adifferent ES/ED section pair.

The functional ring display format of the present invention, as shown inFIG. 14, is advantageous for diagnosing cardiac disease and detectingischemic areas of the myocardium that would otherwise be falselyidentified as an infarct. Suppose arc section 1416 was color codedpurple and was of short width, as shown. This would indicate that thegiven section (section two) of the region of interest that surrounds therelevant short axis image has at least two characteristics. First, themyocardial perfusion is very low (having a low ratio) meaning the tissuedid not uptake much blood when the radionuclide was introduced (i.e.,under the stress condition). Second, the myocardial wall motion is verylow (low width) meaning the tissue is not moving much while heart wasimaged (i.e., at the rest phase during the imaging session of thepresent invention). This would indicate that the area of study maycontain an infarct area because under both stress image computations(perfusion ration ) and rest image computations (wall movement factor)the myocardium illustrates an abnormality.

Further, using the functional display ring of the present invention, anischemic area of the heart may also be detected which might otherwise befalsely diagnosed as an infarct. These areas are characterized asregions having poor myocardial perfusion (of the stress condition) butfair or normal wall movement (detected at the rest condition). Forinstance, assume region 1418 was colored coded purple which correspondsto very low perfusion ratio. However, region 1418 has good movementbecause the width parameter is large, meaning the myocardial tissue ismoving during systole and diastole segments of the cardiac cycle. Suchan area is characteristic of ischemia, where the stress condition(perfusion) illustrates the defect but the rest condition (wall motion)may or may not illustrate the problem because the myocardium functionsnormally at rest.

The present invention is able to detect the above condition without thenecessity of taking two separate imaging sessions (i.e., one at rest andone at stress) which is a requirement of non-gated SPECT studies.Because the present invention functional display ring allows comparisonof information representative of both a rest condition (imaging--wallmovement) and a stress condition (radionuclide introductiontime--perfusion) at the same time, the present invention offers a systemfor accurately and efficiently detecting false positives (i.e., falsedetection of infarct areas). That is, the region 1418 is not an infarctbecause the region moves during imaging, i.e., it has fair wall motion.The gated SPECT imaging technique of the present invention allowssampling of various segments of the cardiac cycle and can thus deliverinformation pertinent to the myocardium movement that non-gated SPECTstudies do not provide. While other systems may predict this region asinfarct because of the low perfusion ratio, the present inventionfunctional ring display illustrates the wall motion from the gated SPECTimaging data and accurately represents that the region is bettercharacterized as ischemic.

Functional ring displays of the present invention also provide a singlequantitative display for detecting areas of radiation attenuation thatmay be falsely identified as infarct areas. Radiation attenuation iscommon in certain areas of the heart for men as a result of thediaphragm. Attenuation is also common for female patients as a result oftissues from the breast. Again, the functional displays will reveal thetrue nature of these areas, because while perfusion ratios may be low asa result of attenuation, wall movement may still be detected anddisplayed within the functional display ring.

Referring back to FIG. 13, the quantify display screen also containsuseful cycle fields and other special indicators. The present inventionallows any of the series of frames in the upper (ED) or lower (ES) rowsto be advanced or decremented using frame advance arrows 1340 and 1342.If the advance or decrement arrow 1382 is activated, each of the shortaxis image frames of the ED series (i.e., 1310, 1314, 1318, 1322, 1226)and each of the ES series (1312, 1316, 1320, 1324, 1328) will incrementby one or decrement by one as the case may be. It is appreciated thatdue to the nature of the quantitative comparison, frames of both ED andES advance or decrement in unison. It is appreciated that the framecycle field 1340 will control how many frames are advanced ordecremented by the present invention. The region cycle field 1355indicates the number of sections each region of interest will be dividedinto. The present invention allows either eight sections (as discussedabove) or 16 sections for smaller sections. It is appreciated that if 16sections are selected the corresponding functional display rings willeach have 16 arc sections per ring, each section representative of ES/EDsection pair. The color region 1356 indicates the particular selectionof colors for the perfusion ratio color table 1372. Using cycle filed1356 different color tables and shading tables may be programmed andselected by the present invention.

Apart from the advantageous display of the functional rings of thequantify screen of the present invention, the user may cine the gatedimages in the first viewport of each of the series for the two displayedsegments (ED and ES). This will display the entire cardiac cycle.

It is appreciated that from the quantity screen processing 940 selectionof the main selection field 1120 returns processing to the main displayscreen. Selection of the 3D 1025 or image 1020 selection fields returnsthe processing to the 3D display processing or image screen processingrespectively. Selection of the graph selection field 1380 transfers theuser to the graph screen processing 950 (described further below). It isappreciated that the quantify screen also displays information as to thepatient name, patient ID and study date.

FIG. 15 illustrates a detailed flow chart of the processing 1510 of thepresent invention used to generate and display the functional displayring images. The computer system 120, under direction of the presentinvention, performs the processing blocks of FIG. 15. The processing1510 is a subset of the processing of block 940 and begins at block1512. At block 1512 the computer system 120 displays N number of imageframes on the display screen 105 of each selected segment. In thetypical case the selected segments represent the ED and ES phases of thecardiac cycle. Five image frames for each segment are displayed andconstitute the ED series and the ES series. Next at block 1514, thecomputer system 120 is instructed by the present invention to allow theuser (via the cursor 5 and the mouse 107) to position or reposition acenter point for a ROI (1351a) on the first short axis image (1310) ofthe end-diastole image frame series and to configure or reconfigure theradius of the ROI to align the circumference of the ROI with the edge ofthe myocardium displayed in the first ED image of the ED image frameseries. At processing block 1516, the computer system 120 is instructedby the present invention to allow the user (via the cursor 5 and themouse 107) to position or reposition a center point for a ROI (1352a) onthe first short axis image (1312) of the end-systole image frame seriesand to configure or reconfigure the radius of the ROI to align thecircumference of the ROI with the edge of the myocardium displayed inthe first ES image of the ES image frame series. At blocks 1514 and1516, each ROI is sectioned into 8 or 16 individual pie shaped sections.

Once the two ROIs have been defined for the first image of the ED and ESimage frame series, the present invention proceeds to block 1518 wherethe ROIs (1351b-h, 1352b-h) are defined for each of the remainder imageframes of the ED and ES image frame series. The ROIs generated in thisstep for the remainder frames of the ED and ES series are defined basedon the placement of the ROIs in the first image frames. Next, at block1520 the present invention displays each region of interest for everyframe of the ED and ES series that are not yet displayed At block 1522the present invention then retrieves (fetches) from memory a first pairof ED and ES images and information regarding their respective regionsof interest. The first image and ROI pair in the example of FIG. 13represent the images within viewports 1310 and 1312.

At block 1524, the perfusion ratios for each of the eight (or 16)sections of the functional display ring are computed by the presentinvention using the associated section pairs from the two receivedregions of interest, one ED and one ES. The functions utilized tocompute these perfusion ratios for each section pair are shown indiscussions above. This process 1524 computes eight (or 16) perfusionratios, one for each corresponding section pair of the ROIs. For eachsection pair, the process 1524 utilizes an average function to averagethe maximum intensity pixels for the current ED section and for thecorresponding current ES section and then divides the ES result by theED result. The perfusion ratios are then entered into a color lookuptable (that may reside in memory 102) and a particular color code isassigned for each ratio (see Table I). The above is done for each of theeight section pairs for each ES/ED segment for the current functionaldisplay of the present invention.

At block 1526, the computer system 120 then computes the wall motion ordisplacement values for each section pair of the current functionaldisplay ring using the corresponding section pairs of the ED and ESregions of interest that were used above in the well perfusioncomputations. The present invention first computes the location of thecenter of mass for each ED section and for each corresponding ES sectionof the input ROIs and then computes a radial distance for each section(using the distance from the center point of the respective ROI to thecomputed center of mass). The computer system 120 then takes thedifference of the radial distances for each section pair ES/ES andequates this value to the displacement factor for the given section; alleight section pairs (ES/ED) are processed in turn. If the radialdistance of the ES section is larger than ED section for given sectionpair then the displacement factor takes a negative sign, otherwise thevalue is positive. This radial difference is computed for all associatedsection pairs of the ED and ES ROIs for the currently processedfunctional display.

At block 1528, the computer system 120 of the present inventiongenerates the current functional display on the computer screen 105according to the image format of FIG. 14. The computer displays alleight of the computed arc sections of the functional display ring using(1) the computed arc width for each section determined by thedisplacement factors of block 1526 and (2) the determined arc colorsfrom the perfusion ratios of block 1524. All eight (or 16) arc sectionsare displayed in a ring format. Next at block 1530, the computer 120checks if there are more functional displays to process. The firstfunctional display 1360 (of FIG. 13) utilizes information from theimages of viewports 1310 and 1312. If there are more ES/ED image pairsto process, the present invention will advance to the next ES/ED pair(viewports 1314 and 1316) and will return to processing block 1522 tofetch the image data for and to render the next functional display ring1362. This process will continue in a cyclic fashion by the presentinvention until the last functional display ring 1365 is rendered usingthe data associated with viewports 1326 and 1328. At this point, theprocessing of block 1530 will recognize that no further functionaldisplays are required for rendering and will flow to the exit or returnprocessing block 1532 which returns to the general processing of block940.

Graph Screen Processing 950. The present invention enters the graphscreen processing 950 upon activation of the graph selection region 1380from the quantify screen processing. The quantify screen processing 940is the only entry point to the graph screen processing 950. The graphscreen of the preferred embodiment of the present invention isillustrated within FIG. 16. The displays within the graph screen allowthe user to graphically review the calculated perfusion ratioinformation in various formats. The first format 1625 is acircumferential plot of the ratios for all eight sections of a selectedfunctional display ring. The second format 1635 is an axis plot of onesingle section through all image frames of the short axis data set

Referring to FIG. 16, there are two rows of one viewport each fordisplay of a selected short axis frame for the ED and ES segments (orany other selected segments that have been reconstructed these are 1610and 1620. Each viewport displays an image with associated ROI which wasdefined in the quantify screen. Viewport 1610 illustrates an oblique EDimage with ROI 1611 and viewport 1620 illustrates an oblique ES imagewith ROI 1621. These particular short axis image frames may beincremented or decremented under user control by selection of theadvance and decrement arrows 1651. It is appreciated that initially theviewports 1610 and 1620 display the ROI and image data represented inviewports 1310 and 1312 of FIG. 13, respectively. If the image framesare advanced, by cursor selection of the arrow 1651, then the framenumbers in both viewports 1610 and 1620 will advance by one, ordecrement by one as the case may be if the decrement arrow was selected.It is appreciated that each time the frames or decrement, thecircumferential plot 1625 will change in association with the framesthat are displayed. The image frames for ED and ES cannot be advancedindependently, the frame number much be matched for both viewports 1610and 1620.

The user may cine either or both of the series images (of viewports 1610and 1620) in gated fashion with the use of cine selection regions withinthe present invention. If the cine function is selected, thecircumferential graph will not update. When the cine is stopped, thecircumferential graph 1625 updates with the frame that is displayed inthe viewport. If only one of the series images is placed in cine motionand then stopped, the series image that was not in motion will advanceto the frame number stopped on by the image that was in motion. Forexample, if viewport 1610 was in cine, viewport 1620 would remain andwhen viewport 1610 exited cine the frame number of 1620 would modify tothe frame number of viewport 1610.

The circumferential graph 1625 plots the ratio values along the verticaland the individual sections along the horizontal for a particularfunctional display ring. In FIG. 16 there are only 8 sections of thefunctional display. This graph is a representation of the calculatedratios of all eight of the arc sections associated with one functionaldisplay ring. The maximum values for the vertical axis are the maximumratio for all frames in the oblique set and do not change from frame toframe. The horizontal axis is the number of the pie shaped sections 1-8.Also displayed on the graph screen is a window display 1640 whichdisplays the raw perfusion data in numeric form according to thespecific eight sections. This is a numeric representation of the ratiodata shown in graph 1625 and the data in the window 1640 will updatewhenever the graph 1625 updates.

The axis graph 1635 is a representation of calculated perfusion ratiosof just one pie shaped section plotted over all of the frames in theshort axis data set. This graph allows a physician to observe all theperfusion ratios for a selected section of a ROI across all short axisimage frames (or "slices") of the short axis dataset for thereconstructed volume. This display can be used to default or verifysuspected abnormal regions of the heart. The vertical axis maximum valueof graph 1635 is the maximum ratio value for all regions for all frames.The horizontal axis represents the number of different image frames("slices") within the short axis dataset. Only 16 slices are displayedat a time for clarity. The range of image frames may be selected usingfields 1673 and 1674. More slices can be displayed in the axis graph byactivation of the more region 1671. These values of the axis graphupdate if the user selects a different pie shaped section for displayusing the cursor 5. Data window 1645 illustrates the ratio data innumeric form that comprise the axis graph 1635 and this data is updatedwhenever the axis graph 1635 is updated.

The present invention allows some parameter modifications for the axisgraph. The region cycle field 1672 is a field that allows the user toselect the pie shaped section to apply to all of the frames for the axisgraph 1635. The choices are from 1 to 16, depending on the number ofsections for a region of interest. The start slice 1673 and end slice1674 cycle regions allow the user to limit the number of image frames ofthe short axis dataset from which the ratio data will be plotted for theaxis graph. The range is from 1 to n (n being the maximum of frames inthe short axis or oblique data set).

Segment selectors 1630 and 1632 are not active in the graph screen. Theuser cannot alter the segments within the graph screen. To change thesesegments, the user must return to the quantify screen and selectsegments. If the user changes segments, then the user is required todefine new ROIs for the segment. It is appreciated that the images ofviewports 1610 and 1620 may be placed in cine gated motion.

Referring to FIG. 16, from the graph screen, activation of main region1120 returns to the main screen processing 910, activation of the imagesregion 1020 returns to the images screen processing 950, activation ofthe 3-D region 1025 returns to the 3-D processing 920 and activation ofthe quantify 1027 screen returns the user to the quantify screenprocessing 940 Activation of the cancel field 1696 cancels the currentfunction and returns the user to the prior display screen processing.

The above system for image acquisition, processing and display, providesa physician a valuable tool for diagnosing cardiac disease. Thefunctional display rings of the preferred embodiment of the presentinvention simultaneously provide quantitative information regarding wallperfusion and wall motion of a selected myocardium structure allowingefficient diagnosis of infarct areas and ischemic areas of themyocardium. Further, such display offers a unique method of detectingotherwise false (infarct) positives. The present invention allows thecapacity to simultaneously observe image data of both stress conditions(wall perfusion) and rest conditions (wall motion) with only one imagingsession, thus eliminating the requirement for a separate rest and stressimaging session. The quantitative displays of wall motion (arc width)and wall perfusion (arc color) provide the physician with valuablequantitative data for the effective diagnosis of cardiac artery disease(CAD). Further, the various display formats of the present inventionoffer the physician a number of qualitative analysis tools. Images canbe displayed, recalled, compared and placed in cine motion for gated andSPECT image data within the present invention. In short, the preferredembodiment of the present invention provides a powerful tool for bothquantitative and qualitative analysis and display of the information ofthe reconstructed volume of the image heart using gated SPECT imagingtechniques and systems.

SECTION V--Semi-List Mode Acquisition

The computer camera system 10 (of FIG. 1) contains a computer systemused for acquisition and processing of image data received from thedetector 12; this computer system may be implemented within a hardwareboard of the computer system 110. It is understood that this computersystem contains at least those elements of FIG. 2 that are indicated byblock 110. To this extent there is a processor, bus, memory unit, inputdevice, data storage device and signal input and output communicationdevice. The camera system 10 utilizes this camera acquisition computersystem to interpret and image data (data events) received directly fromthe imaging detector. The data that the camera acquisition computersystem ("CACS") receives from the camera detector 12 is composed of astream of words (data event words) that are approximately each 32 bitslong and are communicated bit serially. Each word contains: an Xcoordinate store, a Y coordinate store, an energy level, a data/tagflag, and a tag code that 16 types of tags of which four represent 1) Rwave time, 2) start command, 3) stop command, or) a time tag or "tick."These event words are read by the CACS and stored in a memory unit Datain the above form is called "list" data in "list mode" because each ofthe events is individually received and stored into a large listing ofdata in memory. The X and Y coordinate store will indicate the locationof each event, if the word represents data. Also indicated, in thiscase, will be a representation of the energy of the detected event atthe location. The energy bit will be summed with other bits at theindicated (x, y) location of a histogram (discussed below) to determinethe total counts for a given (x, y) location. The data/tag bit indicateswhether or not the word is data or some command tag. The R-wave time tagindicates that the word is the start of a new R wave of data, thisindicates the start word of a heartbeat R-R interval dataset. The startcommand indicates to the CACS that an imaging session is to start. Thestop command then indicates when to interrupt the imaging session. Thetime tag is placed into the data stream at some known interval of time,in the present invention it is introduced every millisecond; it isunderstood that from 4 to 6 event words may be received between eachtime tag. The above list is also referred to as event data in list form

The CACS then, at some point, will take the list data and convert itinto a summarized format, such as a histogram, which records the totalor summation of the event data for a given X, Y coordinate. It isunderstood that the term "histogram" and the term "raw image" areinterchangeable. The summation histogram for a given projection angleand for a given gated segment eventually is passed to the imaging system120 for processing and reconstruction. The present invention semi-listmode acquisition is a method and mechanism to increase the efficiencyand processing power of the CACS in generating the summation histogram(summation raw image) from the input data stream.

In the past, prior art camera systems would perform a first process ofreading in a portion (1/10 or 1/20) of the data representing an R-Rinterval as data event words, parsing the words, and storing themindividually into memory. The system then would then, in real-time withthe above process, parse this acquired portion in a binning procedurethat would, after processing several portions, create a histogram of thecount information per (x, y) location for a given R-R interval of data.After the "beat histogram" was complete, the system would determine,based on the length of the R-R interval, whether the beat was acceptedor rejected. If the R-R interval was rejected, the prior art systemwould erase the beat histogram and continue to process the next R-Rinterval. If accepted, the prior art system would sum the beat histograminto a summation histogram that included the (x, y) data for allaccepted beats for a particular projection angle and gated segment Thissystem is not efficient because for bad beats the computer system mustcompletely parse the event data to create the beat histogram, that willbe ignored and erased. This is terribly inefficient. Further, the dataevents are parsed twice in the prior art, once for storing them intomemory and a second time for binning. Also, because the prior artsystems performing the binning process in real-time, they must pausereceipt of data words in order to perform the summation. This meansprior art systems are unable to collect 100% of the data words for anR-R interval.

Semi-List Mode Acquisition. The present invention solves the aboveproblems by providing a semi-list mode acquisition procedure that isillustrated in FIG. 17A. According to the present invention, the dataevent words that are received by the CACS from the detector input 1710are stored individually into successive addresses of a ring buffer 1720which is part of a memory unit of the CACS. The storage of the receiveddata event words into the ring buffer is accomplished by a first processof the present invention which operates continuously in real-time. Aring buffer and buffering technique are well known in the art ofcomputer processing and utilize a start point 1724 and an end point 1722that may adjust around the ring buffer as data is received andprocessed. The ring buffer 1720 is capable of storing approximately 2 to4 R-R intervals worth of event data. The first process of the presentinvention also examines the data words as they are received in order toprocess the tag commands that may be present within the data stream(i.e., start, stop, etc.). The first process of the present inventionalso detects the start of a new R-R interval and counts the time tagsbetween successive R-R interval markers to determine the duration, inmilliseconds, of a particular R-R interval. This is the duration of agiven imaged heartbeat. With reference to FIG. 17A the first process ofthe present invention constructs the data of the ring buffer 1720.

The first process signals to the second process when an complete R-Rinterval worth of data words have been received and processed by thefirst process. When a complete R-R interval worth of data event wordsare received by the first process, it will perform two very importantfunctions. First, it stores at a memory location (start location 1764)at the beginning of the received R-R interval the address in the ringbuffer of the start word of the next R-R interval that will be or hasbeen received. Also, it records at a memory location (count location1762) at the beginning of the received R-R interval the number of counttags detected for the received R-R interval. This information will beutilized by the second process of the present invention in order todetermine when the event words for a given R-R interval dataset havebeen completely received by the first process.

The second process of the semi-list acquisition mode of the presentinvention constructs the summed histogram 1730 which is stored within amemory device of the computer system. The second process continuallyscans the start address of given R-R interval's set of data event wordsand waits until the set is completely processed by the first process.This is done either by continually polling the count location 1762 untila non-zero value is detected or by continually polling the startlocation 1764 until a non-zero value is detected, or both. When it isdetected that the data event set for a given R-R interval is complete,the second process will perform a critical determination. It determines,based on the count number, whether or not the count for the R-R intervalis within the acceptable duration window. If the count exceeds theacceptable duration then the beat is bad and the dataset of event wordsfor the R-R interval must be rejected. The second process will thenaccess the start location 1762 of the R-R to determine the address ofthe next R-R interval dataset and will go there and poll (as above)until that R-R interval's dataset is completely processed by the firstprocess.

However, if the beat count at count location 1764 is good (i.e., withinthe acceptable R-R interval window) then second process willsuccessively process each data event word in order to bin the data wordsof the given R-R interval into the summation histogram 1730 of FIG.1730. Eventually, when the summation histogram 1730 is complete it willbe stored in storage device 1740 and transferred to the other systems ofthe present invention.

It is appreciated that by providing the beat count in a predeterminedlocation, the present invention provides a mechanism for quicklydetermining if a bad beat has been imaged, and if so, the second processwill skip the data event words for that beat and continue on to the nextR-R interval's dataset of event words. In so doing, the presentinvention does not waste effort in constructing a beat histogram that isnever utilized. Rather, the present invention collects complete datasets(of event words) for R-R intervals and while so doing quickly keeps arunning tally of the timer tags received to determine the duration ofthe R-R wave. There is no need, therefore, to perform the time consumingand processing intensive procedure of creating a beat histogram if theR-R duration is outside the allowable range. Only these datasets ofevent words of good R-R intervals are summed into the summationhistogram by the second process. It is understood that the presentinvention is a "semi-list" data acquisition mode because it stores somedata in list mode (i.e., only a few R-R intervals worth) and theremainder in history mode within the summation histogram 1730. Thesummed histogram is an array of 64×64 or 128×128 memory locations 16bits deep and records counts per (x, y) location based on the event datawords for R-R intervals of acceptable beat duration.

FIG. 17B illustrates the structure of the ring buffer 1720 andindividual event data word sets for R-R intervals. The ring buffer 1720is shown end-to-end with memory locations of the most recently receiveddata event words illustrated on the left. The most recently completedataset of event words is memory string 1760 at (t=0) for reference. Thedataset 1750 is not yet complete events are still being recorded. Adataset becomes complete when the R-wave tag is encountered indicating anew heartbeat cycle is starting. FIG. 17B illustrates four complete R-Rinterval datasets 1760, 1770, 1780 and 1790. The first process is thenoperational near the start of the data stream 1724 because it must read,process and store the data event words as they arrive into the ringbuffer in real-time. FIG. 17B also illustrates the count location 1762and the start address location 1764 for the dataset 1760. Alsoillustrated is the current pointer location of the second process 1765which is polling the start address location of dataset 1760 for anon-zero value. It is appreciated that since dataset 1760 is completelyreceived into the ring buffer the start address location 1764 containsthe address within the ring buffer of the start of the next R-R intervaldataset, or point 1767. It is appreciated that the start addresslocation and count location for dataset 1750 are both zero since thedata is not yet complete. It is also understood that the second processcould also be polling at the start address of dataset 1770 or 1780 or1790 depending on the occurrence of other, previous events. That is tosay, the processing of the second process is not done in real-time, butcan be processing at one, two or three R-R intervals behind the firstprocess.

If, for instance, the count value at 1762 indicated that the duration ofthe beat represented by dataset 1760 was bad then the second process ofthe CACS would skip this dataset by reading the start address from 1764and then jumping to the address indicated by 1767 to process the nextR-R interval, without generating any beat histogram. In this case sincedataset 1750 is not yet complete, the second process would wait or loopuntil the start location or count location were non-zero. On the otherhand, if the count at 1762 indicated that the R-R interval for dataset1760 was good then the second process would individually read each ofthe event words and would bin the data words into the summationhistogram 1730 as required. It is appreciated that the first process ofthe CACS already processed the commands and other tags of the dataset1760. Assuming the second process is currently polling at dataset 1790,if it found a bad beat, it could jump to the next R-R interval 1780 andskip that one too and then process dataset 1770. Given the aboveflexibility of data stored in the ring buffer, the present inventionsemi-list mode acquisition may implement a mechanism for slopping beatinformation that is received before the occurrence of a bad beat. It isunderstood that the binning procedure of the second process of thepresent invention may be implemented using well known binningtechniques.

FIG. 17C is a flow diagram illustrating major processing steps of thesemi-list mode acquisition procedure of the invention. The first process1910, as described above and implemented by the CACS, is illustrated inmore detail flow diagram format. At 1912, the first process receives anevent data word from the input stream from detector 12. At 1914, thereceived data event words are parsed by the processor of the CACS inthat any tags are processed for commands and the data words are storedinto the ring buffer which holds about 3 to 4 R-R intervals worth ofdata event words. At 1916, the processor will tally the number of timercount tags received since the last R-wave tag in order to time theduration of the current R-R interval; the start of a new R-wave is alsoindicted here. At 1918, the processor checks a new R-wave tag islocated. If not, the processor returns to 1912 to continue processingand storing data event words into the ring buffer 1720 for the currentR-R interval dataset.

At block 1920, the processor determined that a new R-wave tag wasdiscovered. The processor then marks the start address of the ringbuffer of where the next R-R interval dataset will begin. At 1922, theprocessor then stores the summation of the timer count tags received forthe current R-R interval dataset and returns to 1912 to collect thisnext dataset. At this point the current R-R dataset is complete and maybe parsed by the second process 1950. The first process 1910 operates inreal-time.

The second process 1950 of the present invention does not function inreal-time but may process R-R interval datasets that were previouslyreceived by 1910. At 1952, the second process polls the start addressand/or the count value (as stored by 1920 and 1922) of a previouslyprocessed R-R dataset from the first process. At 1954, if these valuesare zero then the processor returns to 1952. If the values are not zerothen the R-R interval dataset is complete and ready for the secondprocess 1950. At 1956, the second process examine the count value todetermine if the value is within the allowable window and the beat iscompared at 1958. If the beat is good, then at 1960, the entire R-Rinterval dataset is binned into the summation histogram 1730 for allvalid data for binning. Still at 1960, then the R-R interval dataset isreset and the start address is read for the next R-R interval data andthe process returns to 1952.

If the beat was determined bad (outside the window) at 1958, then at1962 the second process will read the start address of the next R-Rinterval dataset (as stored by 1920). At 1964, the second process willskip the current bad R-R interval dataset, without creating anyhistogram binning, and will jump to that start location within the ringbuffer and enter block 1952. By eliminating the binning of step 1960 atthis point the present invention operates efficiently.

In sum, by providing a first processing system that inputs the dataevents in real-time and records 1) the number of counts received and 2)the start address within the ring buffer of the next R-R interval, thepresent invention provides the binning process (the second process) witha mechanism for skipping bad beats. The second process does not performthe time consuming process of generating a beat histogram of a bad beat,but rather, only processes good beats into the summation histogram 1730.Although the memory requirements for the ring buffer 1720 areapproximately equivalent to the memory requirements of the prior artbeat histogram, the present invention does offer a vast increase inprocessing speed (about three time faster) over prior art parsingsystems. Further, since the binning process of the present invention isnot accomplished in real-time, like the prior art systems, the presentinvention may gather 100% of the R-R interval because it does not haveto pause receipt of the data events in order to bin.

FIG. 18 illustrates a flow diagram of the binning procedure 1800 of thepresent invention which is the same process as block 1960 (of FIG. 17C).The binning procedure first examines each data word of a good R-Rintervals dataset to determine if the data word has data or is empty atstate 1820. If the data word is not empty then the computer checks ifthe data word represents data or a tag; this is done at block 1830. Ifthe data word represents pixel data then the process performs a numberof other various checks that are not pertinent to the present invention.If these series are successful the flow reaches block 1850 where thecomputer determines if binning is required based on the presence ofvalid data for binning. If so, the process flows to block 1860 where thevalid data word is binned into the summation histogram 1730. In priorart systems the process would then flow back to block 1820 to retrieve anew data word. However, the present invention advantageously assumesthat since the current data word contains valid data that needed to bebinned, the next data word may also have valid data to be binned. Thisis usually the case since tags are relatively infrequent within the datastream of event words. Therefore, the present invention at block 1870peeks at the status of the next data word (this is entirely possiblebecause the ring buffer 1720 of the present invention contains the datawords for an entire R-R interval) and if this next data word is datathen the present invention loops directly back to block 1860 to bin thedata. If the test fails at block 1870 then the present invention loopsback to block 1820.

It is understood that by not automatically returning to block 1820 aftercompletion of the processing step 1860 the present invention eliminatesthe need to redundantly execute the parsing steps 1820, 1830 and 1850(and others) when consecutive data words are encountered that containdata for binning. On the down side an extra condition (block 1870) isimposed within the binning process of the present invention. However,since tags are relatively infrequent within the overall data stream, thetime required to execute this extra condition is far outweighed by thesame saved by avoiding the other, preliminary, parsing steps. It is alsonoted that each of the instructions within block 1880 may be placedwithin an instruction cache memory to further increase the operationalspeed of the binning process when the invention receives consecutivedata words having data for binning. The binning process will then onlyexit the cache memory upon detection of a tag within detection block1870.

The preferred embodiment of the present invention, a computerimplemented system for image acquisition, processing and display ofnuclear medicine images, including functional displays simultaneouslypresenting quantitative display information regarding perfusion andfunction and semi-list mode data acquisition capability, is thusdescribed. While the present invention has been described in particularembodiments, it should be appreciated that the present invention shouldnot be construed as limited by such embodiments, but rather construedaccording to the below claims.

What is claimed is:
 1. In a computer system including a display devicefor displaying information, a method for presenting cardiac information,said method comprising:storing individual frames of a reconstructedvolume in a single data structure including a short-axis dataset offrames, a vertical long axis dataset of frames, and a horizontal longaxis dataset of frames; causing a plurality of frames of said short-axisdataset, said vertical long axis dataset and said horizontal long axisdataset to be displayed by said display device for each of at least twoindividual gated segments of a cardiac cycle; causing a userpositionable representation to be displayed by said display device inone frame of one of said datasets; and updating frames of the other twoof said datasets based on a repositioning of said representation.
 2. Amethod as described in claim 1, wherein said updating frames of theother two of said datasets comprises updating frames of the other two ofsaid datasets based on a repositioning by a user of said representation.3. A method as described in claim 1, wherein said representationcomprises a set of user positionable crosshairs.
 4. A method asdescribed in claim 1, wherein said updating frames of the other two ofsaid datasets based on a repositioning of said representation compriseschanging the frames of said other two of said data sets that aredisplayed by the display device based on said repositioning of saidrepresentation.
 5. A method as described in claim 1, wherein said atleast two individual gated segments of said cardiac cycle comprise anend-systole segment and an end-diastole segment of said cardiac cycle.